Effects of Direct Renin Blockade on Renal & Systemic Hemodynamics and on RAAS Activity, in Weight Excess and Hypertension: A Randomized Clinical Trial.

AIM: The combination of weight excess and hypertension significantly contributes to cardiovascular risk and progressive kidney damage. An unfavorable renal hemodynamic profile is thought to contribute to this increased risk and may be ameliorated by direct renin inhibition (DRI). The aim of this trial was to assess the effect of DRI on renal and systemic hemodynamics and on RAAS activity, in men with weight excess and hypertension. METHODS: A randomized, double-blind, cross-over clinical trial to determine the effect of DRI (aliskiren 300 mg/day), with angiotensin converting enzyme inhibition (ACEi; ramipril 10 mg/day) as a positive control, on renal and systemic hemodynamics, and on RAAS activity (n = 15). RESULTS: Mean (SEM) Glomerular filtration rate (101 (5) mL/min/1.73m2) remained unaffected by DRI or ACEi. Effective renal plasma flow (ERPF; 301 (14) mL/min/1.73m2) was increased in response to DRI (320 (14) mL/min/1.73m2, P = 0.012) and ACEi (317 (15) mL/min/1.73m2, P = 0.045). Filtration fraction (FF; 34 (0.8)%) was reduced by DRI only (32 (0.7)%, P = 0.044). Mean arterial pressure (109 (2) mmHg) was reduced by DRI (101 (2) mmHg, P = 0.008) and ACEi (103 (3) mmHg, P = 0.037). RAAS activity was reduced by DRI and ACEi. Albuminuria (20 [9-42] mg/d) was reduced by DRI only (12 [5-28] mg/d, P = 0.030). CONCLUSIONS: In men with weight excess and hypertension, DRI and ACEi improved renal and systemic hemodynamics. Both DRI and ACEi reduced RAAS activity. Thus, DRI provides effective treatment in weight excess and hypertension. TRIAL REGISTRATION: Dutch trial register, registration number: 2532 www.trialregister.nl.

Augmentation of angiotensinogen expression in the proximal tubule by intracellular angiotensin II via AT1a/MAPK/NF-кB signaling pathways.

Long-term angiotensin II (ANG II) infusion significantly increases ANG II levels in the kidney through two major mechanisms: AT1 receptor-mediated augmentation of angiotensinogen (AGT) expression and uptake of circulating ANG II by the proximal tubules. However, it is not known whether intracellular ANG II stimulates AGT expression in the proximal tubule. In the present study, we overexpressed an intracellular cyan fluorescent ANG II fusion protein (Ad-sglt2-ECFP/ANG II) selectively in the proximal tubule of rats and mice using the sodium and glucose cotransporter 2 (sglt2) promoter. AGT mRNA and protein expression in the renal cortex and 24-h urinary AGT excretion were determined 4 wk following overexpression of ECFP/ANG II in the proximal tubule. Systolic blood pressure was significantly increased with a small antinatriuretic effect in rats and mice with proximal tubule-selective expression of ECFP/ANG II (P < 0.01). AGT mRNA and protein expression in the cortex were increased by >1.5-fold and 61 ± 16% (P < 0.05), whereas urinary AGT excretion was increased from 48.7 ± 5.7 (n = 13) to 102 ± 13.5 (n = 13) ng/24 h (P < 0.05). However, plasma AGT, renin activity, and ANG II levels remained unaltered by ECFP/ANG II. The increased AGT mRNA and protein expressions in the cortex by ECFP/ANG II were blocked in AT1a-knockout (KO) mice. Studies in cultured mouse proximal tubule cells demonstrated involvement of AT1a receptor/MAP kinases/NF-кB signaling pathways. These results indicate that intracellular ANG II stimulates AGT expression in the proximal tubules, leading to increased AGT formation and secretion into the tubular fluid, which contributes to ANG II-dependent hypertension.

Aberrant activation of the intrarenal renin-angiotensin system in the developing kidneys of type 2 diabetic rats.

We have previously reported that intrarenal angiotensin II (Ang II) levels are increased long before diabetes becomes apparent in obese Otsuka-Long-Evans-Tokushima-Fatty (OLETF) rats, a model of type 2 diabetes. In this study, we examined the changes in intrarenal renin-angiotensin system (RAS) activity in the developing kidneys of OLETF rats. Ang II contents and mRNA levels of RAS components were measured in male OLETF and control Long-Evans Tokushima (LETO) rats at postnatal days (PND) 1, 5, and 15, and at 4-30 weeks of age. In both LETO and OLETF rats, kidney Ang II levels peaked at PND 1, then decreased during the pre- and post-weaning periods. However, Ang II levels and gene expression of RAS components, including angiotensinogen (AGT), renin, and angiotensin-converting enzyme (ACE), were not significantly different between LETO and OLETF rats. Intrarenal Ang IIcontents further decreased during puberty (from 7 to 11 weeks of age) in LETO rats, bur not in OLETF rats. At 11 weeks of age, kidney Ang II levels, urinary AGT excretion, and mRNA levels of AGT and renin were higher in OLETF rats than in LETO rats, while blood glucose levels were not significantly different between these groups of rats. These data indicate that continued intrarenal expression of Ang II during pubescence contributes to the increases in intrarenal Ang II levels in prediabetic OLETF rats, and is associated with increased intrarenal AGT and renin expression. Inappropriate activation of the intrarenal RAS in the prediabetic stage may facilitate the onset and development of diabetic nephropathy in later life.

Activated intrarenal reactive oxygen species and renin angiotensin system in IgA nephropathy.

Immunoglobulin A (IgA) nephropathy is recognized worldwide as the most common primary glomerulopathy. Although the mechanisms underlying the development of IgA nephropathy are gradually being clarified, their details remain unclear, and a radical cure for this condition has not yet been established. It has been clinically demonstrated that the immunoreactivities of intrarenal heme oxygenase-1 (HO-1) and 4-hydroxy-2-nonenal (4-HNE) markers of reactive oxygen species (ROS) and those of intrarenal angiotensinogen (AGT) and angiotensin II (Ang II) markers of renin angiotensin system (RAS) in IgA nephropathy patients were significantly increased as compared to those of control subjects. In an animal study, high IgA of ddY (HIGA) mice were used as an IgA nephropathy model and compared with BALB/c mice, which served as the control. The levels of markers for ROS (urinary 8-isoprostane and intrarenal 4-HNE), RAS (intrarenal AGT and Ang II), and renal damage in the HIGA mice were significantly increased as compared to those in the BALB/c mice. Moreover, an interventional study using HIGA mice demonstrated that the expressions of 2 lines of intrarenal ROS markers (4-HNE and HO-1), 2 lines of intrarenal RAS markers (AGT and Ang II) and renal damage decreased significantly in HIGA mice receiving treatment with the Ang II receptor blocker olmesartan but not in HIGA mice receiving treatment with RAS-independent antihypertensive drugs (hydralazine, reserpine, and hydrochlorothiazide) when compared with HIGA mice that were not treated. These data suggest that intrarenal ROS and RAS activation plays a pivotal role in the development of IgA nephropathy.

Phylogenetic diversity and similarity of active sites of Shiga toxin (stx) in Shiga toxin-producing Escherichia coli (STEC) isolates from humans and animals.

Nucleotide sequences of Shiga toxin (Stx) genes in STEC from various origins were determined and characterized by phylogenetic analysis based on Shiga toxin (Stx) with those deposited in GenBank. The phylogenetic trees placed Stx1 and Stx2 into two and five groups respectively, and indicated that Stx1 in sheep-origin STEC were placed into a different group from those in other STEC, and that Stx2 of deer-origin STEC also belonged to the unique group and appeared to be distantly related to human-origin STEC. On the other hand, Stx of STEC isolated from cattle, seagulls and flies were closely related to those of human-origin STEC. Such a diversity of Stx suggested that STEC might be widely disseminated in many animal species, and be dependent on their host species or their habitat. In addition, the active sites in both toxins were compared; the active sites in both subunits of Stx in all the animal-origin STEC were identical to those in human-origin STEC, suggesting that all the toxin of STEC from animals might be also cytotoxic, and therefore, such animal-origin STEC might have potential pathogenicity for humans.

Enhancement of angiotensinogen expression in angiotensin II-dependent hypertension.

Chronic infusion of angiotensin (Ang) II leads to the development of hypertension and enhances intrarenal Ang II content to levels greater than can be explained from the circulating concentrations of the peptide. We previously reported that renal angiotensinogen (Ao) mRNA is enhanced in Ang II-dependent hypertension and may contribute to augmented intrarenal Ang II levels, but the Ao protein levels were not significantly increased. Because a high-salt diet (H/S) has been shown to suppress renal expression of Ao mRNA, we examined the effects of chronic Ang II infusion on kidney and liver Ao mRNA and protein levels in male Sprague-Dawley rats (n=12) maintained on an 8% salt diet. Ang II was administered via osmotic minipumps (40 ng/min) to 1 group (n=6) while the remaining rats were sham-operated. A H/S diet alone did not alter systolic blood pressure in sham animals (109+/-6 mm Hg at day 12); however, Ang II infusions to the H/S rats significantly increased systolic blood pressure (167+/-7 at day 12) and intrarenal Ang II content (459+/-107 fmol/g versus 270+/-42) despite a marked suppression of plasma renin activity (0.9+/-0.2 ng Ang I. mL(-1). h(-1) versus 2.8+/-1.3). Ang II infusions significantly increased kidney Ao mRNA compared with the H/S diet alone by 1.9+/-0.1-fold. Western blot analysis of kidney protein extracts showed that the Ang II-infused rats had increased kidney Ao protein levels compared with the H/S diet alone (1.9+/-0.1-fold). Liver Ao mRNA and protein and plasma Ao protein were also significantly increased by Ang II infusions. These data demonstrate the effects of Ang II infusion to stimulate Ao mRNA and protein. Thus, the augmented intrarenal Ang II in Ang II-dependent hypertension may result, in part, by a positive amplification mechanism to activate renal expression of AO:

Detection and characterization of Shiga toxin-producing Escherichia coli from seagulls.

Shiga toxin (Stx)-producing Escherichia coli (STEC) strains isolated from a seagull in Japan were examined. A total of 50 faecal samples was collected on a harbour bank in Hokkaido, Japan, in July 1998. Two different STEC strains, whose serotypes were O136:H16 and O153:H-, were isolated from the same individual by PCR screening; both of them were confirmed by ELISA and Vero cell cytotoxicity assay to be producing active Stx2 and Stx1, respectively. They harboured large plasmids, but did not carry the haemolysin or eaeA genes of STEC O157:H7. Based on their plasmid profiles, antibiotic resistance patterns, pulsed-field gel electrophoresis analysis (PFGE), and the stx genes sequences, the isolates were different. Phylogenic analysis of the deduced Stx amino acid sequences demonstrated that the Stx toxins of seagull-origin STEC were closely associated with those of the human-origin, but not those of other animal-origin STEC. In addition, Stx2phi-K7 phage purified from O136 STEC resembled Stx2phi-II from human-origin O157:H7, and was able to convert non-toxigenic E. coli to STEC. These results suggest that birds may be one of the important carriers in terms of the distribution of STEC.

Characterization of intracellular Ca(2+) increase in response to progesterone and cyclic nucleotides in mouse spermatozoa.

Rises in intracellular Ca(2+) concentration ([Ca(2+)](i)) caused by progesterone, an inducer of the acrosome reaction, or by cyclic nucleotides, possible second messengers, were investigated by Ca(2+) imaging of the head of individual mouse sperm. Progesterone induced a [Ca(2+)](i) rise in a dose-dependent manner (4-40 microM), primarily in the postacrosomal region. For 20-microM progesterone, Ca(2+) responses occurred in 42% of sperm, separated into two types: transient type (60% of responding cells; duration, 1-1.5 min; mean amplitude, 335 nM) and prolonged type (40%; >3 min; 730 nM). Prolonged responses required higher doses of progesterone, and their occurrence was enhanced significantly by preincubation for 2-4 h as compared with transient responses. 8-Bromo-cGMP (0.3-3 mM) induced a [Ca(2+)](i) rise more effectively than did 8-bromo-cAMP. For 1-mM 8-bromo-cGMP, 90% of cells exhibited transient Ca(2+) responses (approximately 1 min; 220 nM), independently of the preincubation time. In Ca(2+)-free medium, most sperm showed no Ca(2+) response to progesterone and 8-bromo-cGMP. Pimozide, a Ca(2+) channel blocker, completely blocked prolonged responses and partially inhibited transient responses. These results suggest that progesterone activates at least two distinct Ca(2+) influx pathways, with fast or slow inactivation kinetics, and some sperm show both types of response. A cyclic nucleotide-mediated process could participate in the progesterone-induced [Ca(2+)](i) rise.

A prospective randomized study comparing endocrinological and clinical effects of two types of GnRH agonists in cases of uterine leiomyomas or endometriosis.

OBJECTIVE: In order to assess the endocrinological changes associated with 2 types of low-dose GnRH agonists depot as well as their clinical efficacy, we performed a randomized prospective comparison study of patients having uterine leiomyomas or endometriosis. METHODS: A prospective randomized study involving 67 patients with uterine leiomyomas or endometriosis was carried out. These patients were randomly administered either buserelin MP 1.8 mg (Group B, n = 34) or leuprolide 1.88 mg (Group L, n = 33). In each group we evaluated the symptoms of genital bleeding and hot flashes during GnRHa treatment, as well as the levels of serum LH, FSH, and estradiol 8 weeks after the start of treatment. In addition, the endometrial thickness was measured by transvaginal ultrasonography, and changes in the volume of the uterine leiomyoma or endometrial cyst at the end of treatment. The GnRHa depot was administered from 3 to 8 times, 28 days apart, in both groups. RESULTS: The incidence of menstruation-like genital bleeding 8 weeks after treatment was significantly (p < 0.01) higher in Group B. However this difference disappeared by 12 weeks after treatment. The climacteric symptom of hot flashes was found to be significantly (p < 0.01) more severe in Group L, and this tendency continued until 20 weeks after treatment. The 2 groups did not differ significantly with regard to the levels of the serum LH, FSH, and estradiol at 8 weeks after treatment or in the endometrial thickness at the end of the GnRHa treatment. In both groups, the volumes of the uterine leiomyomas were significantly (p < 0.01) lower after the treatment. In contrast, the volumes of the endometrial cysts did not decrease after administration of GnRHa in both groups. CONCLUSION: Leuprolide 1.88 induced pituitary down regulation more rapidly than buserelin MP. However the hypoestrogenic symptoms such as hot flashes were more severe in cases treated with leuprolide 1.88 than in those treated with buserelin MP. Our data confirm that the therapeutic efficacy of buserelin MP and leuprolide 1.88 are similar, with both being sufficient to treat uterine leiomyomas and endometriosis.

Altered bile composition in the gallbladder and common bile duct of patients with anomalous pancreaticobiliary ductal junction.

The high incidence of biliary tract carcinoma in patients with anomalous pancreaticobiliary ductal junction (APBDJ) has been well documented. Elevation of the secondary and free bile acid (FBA) concentrations is considered a risk factor for biliary carcinogenesis in these patients. Bile from the gallbladder and common bile duct in 12 patients with APBDJ was analyzed and compared with gallbladder bile from 19 patients with gastric cancer and a normal hepatobiliary tract. The concentrations of secondary bile acids were significantly lower in the APBDJ group than in the control group, and FBA concentrations were not detected in the gallbladder in either group. The lysolecithin (LL) in the phospholipid, which is produced from lecithin by activated phospholipase A(2) in refluxing pancreatic juice, was significantly elevated in the APBDJ group. Elevation of the LL concentration in the bile is one of the factors for the development of biliary tract carcinoma in patients with APBDJ.

Increased activity and expression of Ca(2+)-dependent NOS in renal cortex of ANG II-infused hypertensive rats.

We have previously demonstrated that nitric oxide (NO) exerts a greater modulatory influence on renal cortical blood flow in ANG II-infused hypertensive rats compared with normotensive rats. In the present study, we determined nitric oxide synthase (NOS) activities and protein levels in the renal cortex and medulla of normotensive and ANG II-infused hypertensive rats. Enzyme activity was determined by measuring the rate of formation of L-[(14)C]citrulline from L-[(14)C]arginine. Western blot analysis was performed to determine the regional expression of endothelial (eNOS), neuronal (nNOS), and inducible (iNOS) isoforms in the renal cortex and medulla of control and ANG II-infused rats. Male Sprague-Dawley rats were prepared by the infusion of ANG II at a rate of 65 ng/min via osmotic minipumps implanted subcutaneously for 13 days and compared with sham-operated rats. Systolic arterial pressures were 127 +/- 2 and 182 +/- 3 mmHg in control (n = 13) and ANG II-infused rats (n = 13), respectively. The Ca(2+)-dependent NOS activity, expressed as picomoles of citrulline formed per minute per gram wet weight, was higher in the renal cortex of ANG II-infused rats (91 +/- 11) than in control rats (42 +/- 12). Likewise, both eNOS and nNOS were markedly elevated in the renal cortex of the ANG II-treated rats. In both groups of rats, Ca(2+)-dependent NOS activity was higher in the renal medulla than in the cortex; however, no differences in medullary NOS activity were observed between the groups. Also, no differences in medullary eNOS levels were observed between the groups; however, medullary nNOS was decreased by 45% in the ANG II-infused rats. For the Ca(2+)-independent NOS activities, the renal cortex exhibited a greater activity in the control rats (174 +/- 23) than in ANG II-infused rats (101 +/- 10). Similarly, cortical iNOS was greater by 47% in the control rats than in ANG II-treated rats. No differences in the activity were found for the renal medulla between the groups. There was no detectable signal for iNOS in the renal medulla for both groups. These data indicate that there is a differential distribution of NOS activity, with the Ca(2+)-dependent activity and protein expression higher in the renal cortex of ANG II-infused rats compared with control rats, and support the hypothesis that increased constitutive NOS activity exerts a protective effect in ANG II-induced hypertension to maintain adequate renal cortical blood flow.

Detection of Escherichia coli O157:H7 from Musca domestica (Diptera: Muscidae) at a cattle farm in Japan.

Enterohemorrhagic Escherichia coli (EHEC) O157:H7 was isolated for the first time from Musca domestica L. A total of 310 fly samples was collected from 4 different farms in Obihiro-City, Hokkaido, in the summer and autumn of 1997;5 samples carried E. coli serotype O157:H7. Using ELISA and Vero cell cytotoxicity assay, 3 isolates from 1 cattle farm produced both active Shiga-toxin type 1 (Stx1) and 2 (Stx2). These isolates also carried hemolysin and eaeA genes and harbored the 90-kb virulence plasmid of EHEC O157:H7. Based on plasmid profiles, antibiotic patterns, polymerase chain reaction (PCR)-based DNA finger printing analysis using random amplified polymorphic DNA, pulsed field gel electrophoresis analysis, and DNA sequences of stx1 and stx2, all 3 isolates from fly samples were identical. These results indicate that the house fly is capable of carrying the toxigenic EHEC O157:H7 involved in human disease.

Local renin-angiotensin system contributes to hyperthyroidism-induced cardiac hypertrophy.

We have reported previously that thyroid hormone activates the circulating and tissue renin-angiotensin systems without involving the sympathetic nervous system, which contributes to cardiac hypertrophy in hyperthyroidism. This study examined whether the circulating or tissue renin-angiotensin system plays the principal role in hyperthyroidism-induced cardiac hypertrophy. The circulating renin-angiotensin system in Sprague-Dawley rats was fixed by chronic angiotensin II infusion (40 ng/min, 28 days) via mini-osmotic pumps. Daily i.p. injection of thyroxine (0.1 mg/kg per day, 28 days) was used to mimic hyperthyroidism. Serum free tri-iodothyronine, plasma renin activity, plasma angiotensin II, cardiac renin and cardiac angiotensin II were measured with RIAs. The cardiac expression of renin mRNA was evaluated by semiquantitative reverse transcriptase-polymerase chain reaction. Plasma renin activity and plasma angiotensin II were kept constant in the angiotensin II and angiotensin II+thyroxine groups (0.12+/-0.03 and 0.15+/-0.03 microgram/h per liter, 126+/-5 and 130+/-5 ng/l respectively) (means+/-s.e.m.). Despite stabilization of the circulating renin-angiotensin system, thyroid hormone induced cardiac hypertrophy (5.0+/-0.5 vs 3.5+/-0.1 mg/g) in conjunction with the increases in cardiac expression of renin mRNA, cardiac renin and cardiac angiotensin II (74+/-2 vs 48+/-2%, 6.5+/-0.8 vs 3.8+/-0.4 ng/h per g, 231+/-30 vs 149+/-2 pg/g respectively). These results indicate that the local renin-angiotensin system plays the primary role in the development of hyperthyroidism-induced cardiac hypertrophy.

Mechanism of hyperthyroidism-induced renal hypertrophy in rats.

It is well known that renal hypertrophy is induced by hyperthyroidism; however, the mechanism is not fully understood. We recently reported that cardiac hypertrophy in hyperthyroidism is mediated by enhanced cardiac expression of renin mRNA. The present study addresses the hypothesis that renal hypertrophy in hyperthyroidism is mediated by amplification of renal expression of renin mRNA. Twenty Sprague-Dawley rats were divided into control (n=5) and hyperthyroid groups by daily intraperitoneal injections of saline vehicle or thyroxine. The hyperthyroid group was subdivided further into hyperthyroid-vehicle (n=5), hyperthyroid-losartan (n=5), and hyperthyroid-nicardipine (n=5) groups by daily intraperitoneal injections of saline vehicle, losartan, or nicardipine. All rats were killed at 4 weeks, and the blood and kidneys were collected. The kidney-to-body weight ratio increased in the hyperthyroid groups (+34%). Radioimmunoassays and reverse transcriptase-polymerase chain reaction revealed increased renal renin (+91%) and angiotensin II (+65%) levels and enhanced renal renin mRNA expression (+113%) in the hyperthyroid groups. Losartan and nicardipine decreased systolic blood pressure to the same extent, but only losartan caused regression of thyroxine-induced renal hypertrophy. These results suggest that thyroid hormone activates the intrarenal renin-angiotensin system via enhancement of renal renin mRNA expression, which then leads to renal hypertrophy.

Selective tumoricidal effect of soluble proteoglucan extracted from the basidiomycete, Agaricus blazei Murill, mediated via natural killer cell activation and apoptosis.

We have isolated a novel type of natural tumoricidal product from the basidiomycete strain, Agaricus blazei Murill. Using the double-grafted tumor system in Balb/c mice, treatment of the primary tumor with an acid-treated fraction (ATF) obtained from the fruit bodies resulted in infiltration of the distant tumor by natural killer (NK) cells with marked tumoricidal activity. As shown by electrophoresis and DNA fragmentation assay, the ATF also directly inhibited tumor cell growth in vitro by inducing apoptotic processing; this apoptotic effect was also demonstrated by increased expression of the Apo2.7 antigen on the mitochondrial membranes of tumor cells, as shown by flow-cytometric analysis. The ATF had no effect on normal mouse splenic or interleukin-2-treated splenic mononuclear cells, indicating that it is selectively cytotoxic for the tumor cells. Cell-cycle analysis demonstrated that ATF induced the loss of S phase in MethA tumor cells, but did not affect normal splenic mononuclear cells, which were mainly in the G0G1 phase. Various chromatofocussing purification steps and NMR analysis showed the tumoricidal activity to be chiefly present in fractions containing (1-->4)-alpha-D-glucan and (1-->6)-beta-D-glucan, present in a ratio of approximately 1:2 in the ATF (molecular mass 170 kDa), while the final purified fraction, HM3-G (molecular mass 380 kDa), with the highest tumoricidal activity, consisted of more than 90% glucose, the main component being (1-->4)-alpha-D-glucan with (1-->6)-beta branching, in the ratio of approximately 4:1.

Differential effects of thyroid hormone on renin secretion, content, and mRNA in juxtaglomerular cells.

The effects of thyroid hormone on renin secretion, renin content, and renin mRNA levels in juxtaglomerular (JG) cells harvested from rat kidneys were determined by radioimmunoassays and reverse transcriptase-polymerase chain reaction. Despite a lack of immediate effect, incubation with triiodothyronine dose dependently increased renin secretion during the first 6 h and elevated renin content and renin mRNA levels during the subsequent period. Simultaneous incubation with triiodothyronine and the calcium ionophore A-23187 abolished the increase in renin secretion and attenuated the increase in renin content but did not affect the increase in renin mRNA levels. During simultaneous incubation with triiodothyronine and the adenylate cyclase inhibitor SQ-22536 or membrane-soluble guanosine 3',5'-cyclic monophosphate (cGMP), the increases in renin secretion, content, and mRNA were similar to those observed in the presence of triiodothyronine alone, except for a cGMP-induced attenuation of the increase in renin secretion. These findings suggest that thyroid hormone stimulates renin secretion by JG cells through the calcium-dependent mechanism, whereas the stimulation of renin gene expression by thyroid hormone does not involve intracellular calcium or cyclic nucleotides.

Role of the renin-angiotensin system in cardiac hypertrophy induced in rats by hyperthyroidism.

This study was conducted to examine whether the renin-angiotensin system contributes to hyperthyroidism-induced cardiac hypertrophy without involving the sympathetic nervous system. Sprague-Dawley rats were divided into control-innervated, control-denervated, hyperthyroid-innervated, and hyperthyroid-denervated groups using intraperitoneal injections of thyroxine and 6-hydroxydopamine. After 8 wk, the heart-to-body weight ratio increased in hyperthyroid groups (63%), and this increase was only partially inhibited by sympathetic denervation. Radioimmunoassays and reverse transcription-polymerase chain reaction revealed increased cardiac levels of renin (33%) and angiotensin II (53%) and enhanced cardiac expression of renin mRNA (225%) in the hyperthyroid groups. These increases were unaffected by sympathetic denervation or 24-h bilateral nephrectomy. In addition, losartan and nicardipine decreased systolic blood pressure to the same extent, but only losartan caused regression of thyroxine-induced cardiac hypertrophy. These results suggest that thyroid hormone activates the cardiac renin-angiotensin system without involving the sympathetic nervous system or the circulating renin-angiotensin system; the activated renin-angiotensin system contributes to cardiac hypertrophy in hyperthyroidism.

Thyroid hormone stimulates renin synthesis in rats without involving the sympathetic nervous system.

The present study was performed to examine whether renal expression of the renin gene is regulated by thyroid hormone. Thirty male Sprague-Dawley rats were divided into hypothyroid, control, and hyperthyroid groups by use of daily intraperitoneal administration of methimazole, saline vehicle, or thyroxine, respectively. Each group was further subdivided into sympathetic innervated and sympathetic denervated subgroups by use of intraperitoneal administration of saline vehicle or 6-hydroxydopamine. Plasma renin activity and renal levels of renin were measured by radioimmunoassays after 8 wk. Renal expression of renin mRNA was evaluated by a semiquantitative reverse transcriptase-polymerase chain reaction. Compared with control animals, plasma renin activity, renal level of renin, and renal expression of renin mRNA were reduced (82, 94, and 71%, respectively) in hypothyroid animals and elevated (155, 1,182, and 152%, respectively) in hyperthyroid animals. Sympathetic denervation had no independent effect on these renin values. Our results indicate that thyroid hormone stimulates renin synthesis without involving the sympathetic nervous system.

Schizosaccharomyces pombe is more sensitive to pressure stress than Saccharomyces cerevisiae.

The effects of hydrostatic pressure on ultrastructure, microtubules and microfilaments of Schizosaccharomyces pombe were investigated by fluorescence microscopy, conventional electron microscopy and immunoelectron microscopy. Cells were treated with hydrostatic pressure from 0.1 to 400 MPa for 10 min at room temperature. The nuclear membrane was disrupted at above 100 MPa. At 150 MPa the matrixes of mitochondria had an electron dense area. At 250 MPa the cytoplasmic substances changed dramatically, the cellular organelles could hardly be detected and the fragmented nuclear membrane was barely visible. The fluorescence in alpha-tubulin was lost in most of the cells at 100 MPa. The gold particles for anti alpha-tubulin were not visible in the cells at the same level. Cell cycle specific actin distribution was lost even at 50 MPa, although actin dots localized at the central region remained unchanged. Thick actin cables appeared at 100 MPa. Complete depolymerization of F-actin was observed at 150 MPa. These results suggest that S. pombe cells were more sensitive than Saccharomyces cerevisiae cells. The damage to microtubules and nuclear membrane caused by hydrostatic pressure was though to be followed by breakdown of nuclear division apparatus and the inhibition of nuclear division. This damage might contribute to the frequent formation of polyploidy in S. pombe.