Effects of male sexual maturity of reproductive endpoints relevant to DART studies in Wistar Hannover rats.

Wistar Hannover rats have been utilized as one of major strains in regulatory toxicology studies. This study was performed to verify the appropriate age of male sexual maturity in the development and reproductive toxicity (DART) study in Wistar Hannover rats (RccHan:WIST) by comparing reproductive endpoints between 8, 10 and 12 weeks of ages. Although fertility showed a tendency toward decrease in 8-week-old males, copulation index was not different among three ages. Testis weights reached a plateau at 10 weeks of age, whereas weights of other reproductive organs developed until 12 weeks of age. Indices of spermatogenesis (sperm motility, number of sperm in the epididymis and testis and contents of morphologically abnormal sperm) showed age-related progress and did not fully develop except for 12-week-old. For histology, epididymal tubules in 8-week-old animals showed immaturity with tall epithelium. At cesarean section, dams mated with 8-week-old males showed high incidence of preimplantation loss and the number of live fetuses was less than 10. In conclusion, although reproductive performance attained maturity by age of 10 weeks, spermatogenesis was not fully established at 10-week-old, which could result in a low fertility index. Therefore, we recommend that Wistar Hannover male rats at 12-week-old or older are used to conduct DART study properly and evaluate any adverse effects on dams and embryo-fetal development.

Increase in covalent binding of 5-hydroxydiclofenac to hepatic tissues in rats co-treated with lipopolysaccharide and diclofenac: involvement in the onset of diclofenac-induced idiosyncratic hepatotoxicity.

Diclofenac (DCF), a nonsteroidal anti-inflammatory drug, is well known to induce idiosyncratic hepatotoxicity. Although there remains much to be elucidated about its onset mechanism, it is widely accepted as a hypothesis that idiosyncratic hepatotoxicity arises from a specific immune response to a hapten formed by covalent binding of drugs or their reactive metabolites to hepatic tissues. In this study, we investigated the effects of covalent binding of DCF reactive metabolites to hepatic tissues using a rat model of liver injury induced by co-treatment with lipopolysaccharide (LPS) at a non-hepatotoxic dose. In studies done in vitro using hepatic microsomes prepared from rats treated with LPS alone, 4'- and 5-hydroxylation activities on DCF metabolism and adducts of reactive metabolites to dansyl glutathione (dGSH) were markedly decreased associated with a decrease in total P450 content. However, in studies done in vivo, the LPS/DCF co-treatment significantly increased adducts of 5-hydroxydiclofenac (5-OH-DCF) to rat hepatic tissues and delayed the elimination of 5-OH-DCF from plasma. Furthermore, we investigated the effects of co-treatment on hepatic GSH level in rats. A decrease of hepatic GSH was observed with the LPS/DCF co-treatment but not with LPS or DCF alone. The results suggest that covalent binding of reactive metabolites via 5-OH-DCF to hepatic tissues may play an important role in the onset of DCF-induced idiosyncratic hepatotoxicity, especially under decreased GSH conditions.

Comparison of the effects of four α1-adrenoceptor antagonists on ejaculatory function in rats.

OBJECTIVE: To compare the effects of four α(1)-adrenoceptor (AR) subtype-selective antagonists on ejaculatory function in rats to investigate whether the differences in their modes of action-based on their selectivities for the α(1A)-AR subtype-would be related to the prevalence of ejaculation disorder (EjD). METHODS: The effects of α(1)-AR antagonists on noradrenaline-induced contractions were studied in rat isolated seminal vesicles, vas deferens, bladder trigone, and prostate. Male rats were given α(1)-AR antagonists orally and, 1 hour after the drug administration they were cohoused in pairs for 1 hour with untreated female rats certified to be in estrus. The number of copulatory plugs (NP) present after mating was measured as a marker of EjD. Drug effects on ejaculatory function (ie, on NP) were compared with those on the prostatic urethra (ie, phenylephrine-induced increase in intraurethral pressure [IUP]). RESULTS: All α(1)-AR antagonists concentration-dependently inhibited noradrenaline-induced contraction in all 4 tissues, and there were no differences in the rank order of potencies (tamsulosin > silodosin > alfuzosin > naftopidil) among the tissues. All α(1)-AR antagonists dose-dependently decreased NP and inhibited the phenylephrine-induced increase in IUP. There was little difference in the dose ratio ID(50) value (dose required to produce 50% inhibition) for NP/ID(50) value for IUP response among the four drugs. Drug potencies associated NP and IUP correlated closely with affinities for the human α(1A)-AR. CONCLUSION: α(1)-AR antagonists cause EjD as a class effect that depends on affinity for α(1A)-AR. Differences in α(1A)-AR selectivity would be unlikely to be related to the incidence of EjD.

Spontaneous Subcutaneous Sarcoma in a 50-week-old Male Wistar Hannover GALAS Rat.

A subcutaneous mass was noted in the abdomen of a 50-week-old male Wistar Hannover GALAS rat. Histologically, the tumor was composed of vimentin-positive small round cells with scant cytoplasm arranged in a trabecular, sheet or pericytoma-like pattern and spindle cells arranged in a bundle pattern and vimentin-negative round cells proliferating in an island-shaped pattern. Argentophilic thin fibers were observed to wrap up the individual cells, and some of the tumor cells showed coexpression of vimentin and cytokeratin that formed juxtanuclear globes in the cytoplasm by double immunohistostaining. Transmission electron microscopy did not reveal any characteristic features suggesting cellular differention toward a specific cell type. Based on these findings, it was difficult to specify the origin, and the tumor was diagnosed as a poorly differentiated mesenchymal tumor and classified as a sarcoma, NOS (not otherwise specified).

ß3-adrenoceptor-mediated increased circulating transaminase levels in mice treated with its agonist BRL 37344.

Treatment with the selective ß(3)-adrenoceptor agonist BRL 37344 increased circulating levels of alanine transaminase (ALT) and aspartate transaminase (AST) in mice without causing hepatocellular injury. To clarify whether this was a ß(3)-adrenoceptor-mediated effect, the inhibitory effect of the selective ß(3)-adrenoceptor antagonist SR 59230A on the increase in circulating transaminase levels induced by BRL 37344 was examined. A single intraperitoneal dose of BRL 37344 alone initially increased insulin and non-esterified fatty acid (NEFA) dose-proportionally at 0.5 hr post-dose, findings considered attributable to ß(3)-adrenoceptor-stimulating effects. Levels of the gluconeogenic precursors pyruvate (PA) and lactate (LA) were increased corresponding to the change in insulin. Thereafter, glucose (GLU) level was decreased at 4 and 8 hr post-dose, suggesting disruption of glucose homeostasis. In association with these changes in glucose metabolism, transaminase levels were increased maximally at 4 hr post-dose. The transaminase changes were not accompanied by increases in circulating levels of other hepatocellular enzymes, including guanine deaminase (GUA), glutamate dehydrogenase (GLDH), and lactate dehydrogenase (LDH), or any morphological hepatocellular injury. Intraperitoneal pre-treatment with SR 59230A partly inhibited the effects of BRL 37344 alone, indicating that the increase in levels of circulating ALT by BRL 37344 was attributable to a ß(3)-adrenoceptor-stimulating effect. In conclusion, the ß(3)-adrenoceptor agonist BRL 37344 was shown to increase circulating transaminase levels in mice accompanied with dynamic changes in glucose metabolism. These findings suggest the possibility that circulating transaminase levels are increased as pharmacological effects of drugs disrupting glucose metabolism, and that hepatotoxic markers should be selected considering these effects to distinguish between acceptable pharmacology and toxicity.

Salbutamol inhibits lipopolysaccharide-induced inflammatory responses in rat peritoneal macrophages.

Acute and chronic inflammatory diseases are associated with the induction of inducible nitric oxide synthase (iNOS) and inducible heme oxygenase (HO-1). These inducible enzymes are up-regulated in macrophages subjected to inflammatory stimuli and oxidative stress. beta(2)-Adrenoceptor (AR) agonists, which function as bronchial dilators, are widely used for the treatment of asthma and chronic obstructive pulmonary disease (COPD). We examined whether salbutamol, a classical beta(2)-AR agonist, inhibits the induction of proinflammatory cytokines and stress inducible proteins. Rat macrophages obtained from the abdominal cavity were incubated with lipopolysaccharide (LPS) with or without salbutamol. Induction by LPS of tumor necrosis factor (TNF)-alpha and interleukin (IL)-6 was significantly inhibited (P < 0.05) by salbutamol treatment. Induction by LPS of iNOS mRNA and protein was also significantly inhibited (P < 0.05) by salbutamol. LPS-mediated increases in HO-1 mRNA and protein were not appreciably affected by salbutamol. One of the anti-inflammatory mechanisms of salbutamol was thus found to be inhibition of induction by LPS of extracellular stimulus-responsive kinase (ERK) 1/2 in macrophages. These findings suggest that salbutamol has the potential for use as an anti-inflammatory agent due to its suppression of LPS-induced TNF-alpha, and IL-6 and iNOS via ERK pathway without affecting HO-1 expression.

Successful drug development despite adverse preclinical findings part 2: examples.

To illustrate the process of addressing adverse preclinical findings (APFs) as outlined in the first part of this review, a number of cases with unexpected APF in toxicity studies with drug candidates is discussed in this second part. The emphasis is on risk characterization, especially regarding the mode of action (MoA), and risk evaluation regarding relevance for man. While severe APFs such as retinal toxicity may turn out to be of little human relevance, minor findings particularly in early toxicity studies, such as vasculitis, may later pose a real problem. Rodents are imperfect models for endocrine APFs, non-rodents for human cardiac effects. Liver and kidney toxicities are frequent, but they can often be monitored in man and do not necessarily result in early termination of drug candidates. Novel findings such as the unusual lesions in the gastrointestinal tract and the bones presented in this review can be difficult to explain. It will be shown that well known issues such as phospholipidosis and carcinogenicity by agonists of peroxisome proliferator-activated receptors (PPAR) need to be evaluated on a case-by-case basis. The latter is of particular interest because the new PPAR α and dual α/γ agonists resulted in a change of the safety paradigm established with the older PPAR α agonists. General toxicologists and pathologists need some understanding of the principles of genotoxicity and reproductive toxicity testing. Both types of preclinical toxicities are major APF and clinical monitoring is difficult, generally leading to permanent use restrictions.

Successful drug development despite adverse preclinical findings part 1: processes to address issues and most important findings.

Unexpected adverse preclinical findings (APFs) are not infrequently encountered during drug development. Such APFs can be functional disturbances such as QT prolongation, morphological toxicity or carcinogenicity. The latter is of particular concern in conjunction with equivocal genotoxicity results. The toxicologic pathologist plays an important role in recognizing these effects, in helping to characterize them, to evaluate their risk for man, and in proposing measures to mitigate the risk particularly in early clinical trials. A careful scientific evaluation is crucial while termination of the development of a potentially useful drug must be avoided. This first part of the review discusses processes to address unexpected APFs and provides an overview over typical APFs in particular classes of drugs. If the mode of action (MoA) by which a drug candidate produces an APF is known, this supports evaluation of its relevance for humans. Tailor-made mechanistic studies, when needed, must be planned carefully to test one or several hypotheses regarding the potential MoA and to provide further data for risk evaluation. Safety considerations are based on exposure at no-observed-adverse-effect levels (NOAEL) of the most sensitive and relevant animal species and guide dose escalation in clinical trials. The availability of early markers of toxicity for monitoring of humans adds further safety to clinical studies. Risk evaluation is concluded by a weight of evidence analysis (WoE) with an array of parameters including drug use, medical need and alternatives on the market. In the second part of this review relevant examples of APFs will be discussed in more detail.

Renoprotective effect of the L/N-type calcium channel antagonist cilnidipine on puromycin aminonucleoside-induced nephrosis in rats.

The renoprotective effect of cilnidipine ((+/-)-2-methoxyethyl 3-phenyl-2(E)-propenyl 1,4-dihydro-2,6-dimethyl-4-(3-nitrophenyl)-3,5-pyridinedicarboxylate, CAS 132203-70-4), a L/N-type calcium channel antagonist, on puromycin aminonucleoside (PAN)-induced nephrosis was investigated in rats. In the Experiment I, rats were given an intravenous injection of PAN (70 mg/kg). Cilnidipine (3 mg/kg/day) and enalapril (CAS 75847-73-3, 5 mg/kg/day) were administered orally from 6 days after treatment with PAN (day 6) to day 26, and urinary analysis was performed on days 9, 15, 20 and 27. In the Experiment II, nephrosis was also induced by intravenous injection of PAN (70 or 100 mg/kg) in rats which were treated with cilnidipine and enalapril from days 6 to 10. Systolic blood pressure was measured on day 7 and urinary analysis was performed on day 10. On day 11, serum was collected and the kidneys were removed for immunofluorescence staining for nephrin and podocin proteins. In PAN-treated rats, the daily urinary protein excretion was dramatically elevated on day 5, reached a peak on day 9 and gradually returned to a normal level from days 15 to 27. Cilnidipine (3 mg/kg/ day) significantly suppressed the increase in proteinuria on day 9 and also improved the decrease in creatinine clearance without evident effect on the blood pressure. Furthermore, the elevations in serum total cholesterol and triglyceride tended to be suppressed by cilnidipine. The expression of nephrin and podocin proteins in PAN-treated rats showed the granular pattern in the glomeruli, while the intensity of staining seemed to be dependent on the urinary protein excretion level in the cilnidipine-treated rats. The results obtained in this study suggest a renoprotective effect of cilnidipine in PAN-induced nephrosis in rats.

Collaborative work on evaluation of ovarian toxicity. 2) Two- or four-week repeated dose studies and fertility study of mifepristone in female rats.

In order to assess ovarian pathological changes and their relationship to changes in female fertility parameters, mifepristone, a progesterone receptor antagonist, was selected as the test article and was administered orally to female rats at dose levels of 0, 0.8, 4, 20 and 100 mg/kg for 2 or 4 weeks in repeated dose-toxicity studies and in a female fertility study at dose levels of 0, 0.8, 4 and 20 mg/kg from > 2 weeks before copulation to postcoital day 7. In the repeated dose toxicity studies, persistent estrus was seen in the vaginal smears, and multiple cysts in the ovaries at necropsy, increases in luteinized cysts and hypertrophy of previously formed corpora lutea were observed in the histopathological examination of ovaries in rats receiving 20 mg/kg or more for 2 or 4 weeks. In female fertility studies, persistent vaginal cornification was also observed at 20 mg/kg and the precoital interval was significantly shortened. All of the animals were completely infertile when dosed with 20 mg/kg during the post-coital period. An increase in pre-implantation losses was observed in the animals treated with 20 mg/kg during the pre-coital phase, while treatment with 4 mg/kg mifepristone during the post-coital phase induced an increase in post-implantation losses. These results suggested that a 2-week administration period would be sufficient to detect the ovarian toxicity of mifepristone in repeated dose toxicity study and the pathological findings in the ovaries would reflect the alterations in female reproductive endpoints in the female fertility study.

Embryonic mortality and intrauterine growth retardation (IUGR) associated with placental alterations in pregnant rats treated with methyl methanesulfonate (MMS) at the peri-implantation stage.

Embryonic mortality and intrauterine growth retardation (IUGR) are induced by exposure of rodents to xenobiotic agents during the pregastrulation period of development. We examined the time course of the effects of methyl methanesulfonate (MMS), an alkylating agent, on conceptus development in order to clarify the relative roles of the embryo and the placenta in their induction. Pregnant rats were treated orally with a single dose of MMS (200 mg/kg) in the morning of gestation day (GD) 6 (peri-implantation stage). Embryonic mortality was increased on GD12 and thereafter by MMS treatment, with newly dead embryos showing placental hypoplasia at GD12. Embryo or fetal weight was also smaller for MMS-treated dams than for control dams from GD14 to GD20. The labyrinth zone and junctional zone (JZ) of the placenta were thinner in MMS-treated rats from GD12 to GD17 and from GD12 to GD20 (except for GD17), respectively. Furthermore, MMS-treated dams showed a smaller number of glycogen cells in the JZ on GD14. In contrast, the placental glycogen concentration was higher and the expression of glucose transporter 1 in the JZ remained at GD20. These results indicate that exposure of pregnant rats to MMS at the peri-implantation stage of embryogenesis affects placental development and growth. The placental impairment induced by MMS was likely responsible for the embryonic death observed 6 days after exposure of dams to this agent as well as for the IUGR of surviving embryos or fetuses throughout the gestation period.

Strain differences in hepatic cytochrome P450 1A and 3A expression between Sprague-Dawley and Wistar rats.

Expression of hepatic cytochrome P450 (CYP) isoforms was compared in Sprague-Dawley (SD) and Wistar (WI) rats, which are commonly used strains in preclinical studies. Basal CYP1A1, CYP1A2, and CYP3A2 mRNA levels were higher in WI rats than in SD rats (by 8-, 3- and 2-fold, respectively). Treatment with phenobarbital, a potent CYP inducer, increased the predominance of expression of these three mRNAs in WI rats (by 26-, 4-, and 2-fold, respectively) along with the predominance of increased microsomal total P450 contents and smooth-surface endoplasmic reticulum in the centrilobular hepatocytes. CYP1A enzymatic activity was also higher in WI rats than in SD rats. No strain differences were observed in phenobarbital induction of CYP2B1/2, CYP2C6, or CYP3A1. CYP3A2 mRNA was more strongly induced by dexamethasone, a typical inducer of CYP3A, together with CYP3A1 mRNA, in WI rats than in SD rats (by 2-fold), whereas the CYP1A1 and CYP1A2 mRNA expression induced by beta-naphtoflavone, a typical inducer of CYP1A, did not differ between the two strains. Furthermore, WI rats exhibited predominantly arylhydrocarbon receptor, pregnane X receptor, and constitutive androstane receptor mRNAs, responsible for CYP1A or CYP3A induction, with phenobarbital or dexamethasone induction. In conclusion, significant, predominant expression of hepatic CYP1A and CYP3A mRNAs in WI rats was observed, possibly related to nuclear receptor-mediated induction. Considering the pharmacokinetic and toxicological importance of CYP1A and CYP3A, different outcomes might arise depending on the rat strains used in preclinical studies of drugs metabolized typically or mainly by both isoforms.

Bezafibrate prevents hepatic stellate cell activation and fibrogenesis in a murine steatohepatitis model, and suppresses fibrogenic response induced by transforming growth factor-beta1 in a cultured stellate cell line.

AIM: The aim of this study was to investigate the preventive actions of bezafibrate against non-alcoholic steatohepatitis (NASH), the activation of hepatic stellate cells (HSC), and fibrogenesis by using a model of NASH and an in vitro model. METHODS: Male KK-A(y)/TaJcl (KK-A(y)) mice were fed a methionine and choline-deficient (MCD) diet or a MCD diet containing bezafibrate or pioglitazone for 7 weeks, after which biochemical parameters, pathological changes, and hepatic mRNA levels were assessed. An in vitro HSC model was designed by using a previously described RI-T cell line stimulated by transforming growth factor-beta1 (TGF-beta1). RESULTS: MCD diet-fed KK-A(y) mice developed hepatic steatosis, oxidative stress, inflammation, and hepatic fibrosis. Bezafibrate markedly decreased the hepatic content of triglyceride accumulation of fatty droplets within hepatocytes, and increased the expression of hepatic fatty acid beta-oxidative genes in MCD diet-fed KK-A(y) mice. Bezafibrate markedly inhibited the increases in the plasma alanine aminotransferase level and hepatic content of thiobarbituric acid-reactive substances in this model. Moreover, it dramatically reduced hepatic inflammatory changes and fibrosis concomitantly with marked reductions in the mRNA levels for inflammatory cytokine, chemokine, and profibrogenic genes. Importantly, both bezafibrate and pioglitazone markedly reduced the mRNA levels of profibrogenic and fibrogenic genes in TGF-beta1-stimulated cells. CONCLUSION: Bezafibrate improved hepatic steatosis and potently prevented inflammation, oxidative stress, HSC activation, and fibrogenesis in the liver. Moreover, this study was the first to demonstrate that bezafibrate directly inhibits hepatic fibrogenic response induced by TGF-beta1 in vitro. Hence bezafibrate may be a new therapeutic strategy against NASH and hepatic fibrosis.

Diluted isoflurane as a suitable alternative for diethyl ether for rat anaesthesia in regular toxicology studies.

Despite its explosive properties and toxicity to both animals and humans, diethyl ether is an agent long used in Japan in the anaesthesia jar method of rat anaesthetises. However, in response to a recent report from the Science Council of Japan condemning diethyl ether as acceptable practice, we searched for an alternative rat anaesthesia method that provided data continuous with pre-existing regular toxicology studies already conducted under diethyl ether anaesthesia. For this, we examined two candidates; 30% isoflurane diluted with propylene glycol and pentobarbitone. Whereas isoflurane is considered to be one of the representatives of modern volatile anaesthetics, the method of propylene glycol-diluted 30% isoflurane used in this study was our modification of a recently reported method revealed to have several advantages as an inhalation anaesthesia. Intraperitoneal pentobarbitone has long been accepted as a humane method in laboratory animal anaesthesiology. These 2 modalities were scrutinized in terms of consistency of haematology and blood chemistry with previous results using ether. We found that pentobarbitone required a much longer induction time than diethyl ether, which is suspected to be the cause of fluctuations in several haematological and blood chemical results. Conversely, only calcium ion concentration showed a slight difference from traditional results in the case of 30% isoflurane. Additionally, serum prolactin and corticosterone levels indicated that 30% isoflurane induced less stress than ether, confirming that 30% isoflurane can both provide results consistent with diethyl ether, while at the same time remove its disadvantages. As such 30% isoflurane appears to be a strong alternative anaesthetic agent for future regular toxicology studies in Japan.

Tranilast suppresses the disease development of the adjuvant- and streptococcal cell wall-induced arthritis in rats.

This study explores the effects of the anti-allergic and anti-fibrotic agent tranilast on adjuvant- and streptococcal cell wall-induced arthritis in rats, animal models of rheumatoid arthritis in humans. Tranilast (150 or 300 mg/kg, twice daily) or vehicle only was administered orally to the two arthritis models, from 17 days before sensitization. As a comparative control, methotrexate (0.1 mg/kg, once daily) was given to another group. Tranilast suppressed the increase in foot volumes, paw thicknesses, clinical scores, and histopathological scores of the ankle joints in both models dose-dependently. In addition, the fibrosis indices of the ankles were dramatically decreased by tranilast in both of the models. Compared to the effects of methotrexate, tranilast seemed to work more effectively in the streptococcal cell wall-induced arthritis model than in the adjuvant-induced arthritis model. From these observations, it can be concluded that tranilast suppresses the development of arthritis in multiple models and is potentially a novel therapeutic agent for human rheumatoid arthritis.

Induction of metallothionein by manganese is completely dependent on interleukin-6 production.

Metallothionein (MT) is a cysteine-rich protein that binds to and is inducible by heavy metals such as cadmium and zinc. However, the precise mechanism of MT induction by other metals remains unclear. In the present study, we investigated the mechanism of MT induction by manganese, focusing on the involvement of cytokine production. Administration of MnCl(2) to mice resulted in the induction of MT dose-dependently in the liver with little accumulation of manganese. Speciation analysis of metals in the liver cytosol showed that the major metal bound to the induced MT was zinc. Administration of MnCl(2) caused an increase in mRNA levels of interleukin-6 (IL-6) in the liver as well as an increase in serum levels of IL-6 but not those of other inflammatory cytokines. Subsequently, serum levels of serum amyloid A (SAA), an acute-phase protein induced by IL-6, increased with a peak at 24 h. However, no increase in serum alanine aminotransferase activity was observed, suggesting that manganese enhanced the production of IL-6 and SAA without causing liver injury. In response to IL-6, the expression of a zinc transporter, ZIP14, was enhanced in the liver, possibly contributing to the synthesis of hepatic zinc-MT. In IL-6-null mice, the induction of hepatic MT by treatment with MnCl(2) was completely suppressed to the control level. These results suggest that manganese is a unique metal that induces the synthesis of hepatic MT completely depending on the production of IL-6 without accompanying liver injury.

Differential susceptibility of rat embryos to methyl methanesulfonate during the pregastrulation period.

The effects of exposure of pregnant rats to methyl methanesulfonate (MMS), an alkylating agent, during the pregastrulation period on embryonic and placental development were investigated. SD rats were treated orally with a single dose of MMS (200 mg/kg) in the morning of gestation days 0, 1, 2, 3, 4, 5, or 6 (GD0 to GD6 groups, respectively). The uterine contents including fetuses and placentas of the dams were examined on gestation day 20. The individual fetuses and placentas were weighed, and the fetuses were examined for external, visceral and skeletal anomalies. The progress of ossification was also evaluated. Both pre- and postimplantation embryonic mortalities were higher in the GD0 group than in the control group. The postimplantation loss was also increased for the GD3, GD4 and GD6 groups. Fetal malformations were rare in survivors of all the MMS-treated groups. Intrauterine growth retardation was apparent for fetuses in groups GD5 and GD6. In addition, placental weight was reduced in the GD6 group, but it was increased in the GD0 group. Effects of MMS on embryonic mortality or on fetal or placental growth were absent or minimal in the GD1 and GD2 groups. These results suggest that the susceptibility of rat embryos to MMS varies during the pregastrulation period.

Pentavalent vanadium induces hepatic metallothionein through interleukin-6-dependent and -independent mechanisms.

Metallothionein (MT) is a low-molecular-weight cysteine-rich protein which has a high affinity for metals. The synthesis of MT is induced by heavy metals such as cadmium and zinc. However, little is known about the induction of MT by tetravalent or pentavalent metals. We investigated the induction of MT synthesis by a pentavalent vanadium compound in mice. Hepatic MT concentrations were increased by subcutaneous injection of ammonium metavanadate (AMV) dose-dependently, and to the similar levels as those induced by zinc chloride. However, accumulation of vanadium in the liver was very low, while high concentrations of vanadium were detected in the kidney. High performance liquid chromatography/inductively coupled argon plasma-mass spectrometry (HPLC/ICP-MS) chromatogram of the liver cytosol of AMV-treated mice revealed that the major metal bound to MT was not vanadium, but zinc. The chromatogram of the liver cytosol of MT null mice demonstrated the existence of a low-molecular-weight vanadium-binding protein that is different from MT. A time-course study showed that concentrations of serum interleukin-6 (IL-6) and serum amyloid A (SAA), an acute-phase protein, increased after the AMV injection. To confirm the involvement of IL-6 in MT induction by AMV administration, IL-6 null and wild-type mice were injected with AMV. In IL-6 null mice, hepatic MT induction by AMV administration decreased significantly to about a half of wild-type mice. These data suggest that both IL-6-dependent and -independent mechanisms are involved in MT induction by vanadium compounds in mice.

Effects of bezafibrate, PPAR pan-agonist, and GW501516, PPARdelta agonist, on development of steatohepatitis in mice fed a methionine- and choline-deficient diet.

We evaluated the effects of bezafibrate, a peroxisome proliferator-activated receptor (PPAR) pan-agonist, and GW501516, a PPARdelta agonist, on mice fed a methionine- and choline-deficient (MCD) diet, a model of non-alcholic steatohepatitis (NASH), to investigate (a) the efficacy of bezafibrate against non-alcholic steatohepatitis and (b) the relation between non-alcholic steatohepatitis and the functional role of PPARdelta. Bezafibrate (50 or 100 mg/kg/day) and GW501516 (10 mg/kg/day) were administered by gavage once a day for 5 weeks. Hepatic lipid contents, plasma triglyceride, high density lipoprotein (HDL)-cholesterol and alanine aminotransferase (ALT) concentrations were evaluated, as were histopathological changes in the liver and hepatic mRNA expression levels. Bezafibrate and GW501516 inhibited the MCD-diet-induced elevations of hepatic triglyceride and thiobarbituric acid-reactants contents and the histopathological increases in fatty droplets within hepatocytes, liver inflammation and number of activated hepatic stellate cells. In this model, bezafibrate and GW501516 increased the levels of hepatic mRNAs associated with fatty acid beta-oxidation [acyl-CoA oxidase (ACO), carnitine palmitoyltransferase-1 (CPT-1), liver-fatty acid binding protein (L-FABP) and peroxisomal ketothiolase], and reduced the levels of those associated with inflammatory cytokines or chemokine [transforming growth factor (TGF)-beta1, interleukin (IL)-6, IL-1beta, monocyte chemoattractant protein (MCP)-1, tumor necrosis factor (TNF) alpha and nuclear factor (NF)-kappaB1]. In addition, bezafibrate characteristically reduced the elevation in the level of plasma ALT, but enhanced that in plasma adiponectin and increased the mRNA expression levels of its receptors (adiponectin receptors 1 and 2). These results suggest that (a) bezafibrate (especially) and GW501516 might improve hepatic steatosis via an improvement in fatty acid beta-oxidation and a direct prevention of inflammation, (b) treatment with a PPARdelta agonist might improve non-alcholic steatohepatitis, (c) bezafibrate may improve non-alcholic steatohepatitis via activation not only of PPARalpha but also of PPARdelta, because bezafibrate is a PPAR pan-agonist.

[Toxicity profile of silodosin (KMD-3213)].

The toxicity profile of silodosin, a selective alpha(1A)-adrenoceptor antagonist, was evaluated. The lethal doses were 800 mg/kg in rats and 1500 mg/kg in dogs. Repeated-dose studies revealed fatty degeneration of hepatocytes and an induction of drug-metabolizing enzymes at 15 mg/kg/day or more in male rats, mammary gland hyperplasia at 60 mg/kg/day or more in female rats, and degeneration of the seminiferous tubular epithelium at 25 mg/kg/day or more only in young dogs. Silodosin was negative in all mutagenicity studies, except for a weak positive in a chromosomal aberration assay conducted without metabolic activation. In carcinogenicity studies, mammary gland tumors and pituitary adenomas were increased in female mice given 150 mg/kg/day or more and 400 mg/kg/day respectively, while thyroid follicular cell carcinoma was increased in male rats given 150 mg/kg/day. Reproductive studies in rats revealed a decreased male fertility at 20 mg/kg/day or more and a prolonged estrous cycle at 60 mg/kg/day or more. Silodosin did not exhibit any teratogenic potential in either rats or rabbits, and had no effects on the postnatal development of rat offspring. In safety pharmacology studies, silodosin produced no severe effects on the central nervous, cardiovascular, or respiratory systems. In conclusion, silodosin exhibited adequate safety margins between the clinically recommended dose and those at which toxic effects or safety pharmacological changes were detected. As a new therapeutic drug for the micturition difficulties caused by benign prostatic hyperplasia, silodosin should have few serious side effects in clinical use.