Nonlinear pharmacokinetics of TAK-044, a new endothelin antagonist, in rats.

The mechanism of the nonlinear pharmacokinetics of TAK-044 in rats was shown from in vivo and in vitro studies to be due to capacity-limited hepatic uptake. In the rats, which were given intravenous injections of (14)C-labeled TAK-044 ([(14)C]TAK-044) (1, 3, 10, 30 and 100 mg/kg), the AUC(inf) per unit dose of unchanged compound increased remarkably. An analysis model indicated that the CL(tot), V(1) and k(12) values of TAK-044 decreased significantly with increasing dose, whereas the k(el) values remained constant over the doses examined. The uptake clearance of [(14)C]TAK-044 by several tissues was investigated by an integration plot at doses from 0.3 to 60 mg/kg. This study showed that the liver played the principal role in the removal of TAK-044 from the plasma, while hepatic uptake was capacity-limited at doses greater than 30 mg/kg. The hepatic uptake study using rat hepatocytes indicated that a carrier-mediated transport system contributed to the hepatic uptake of TAK-044, and this system had high affinity (K(m,in vitro); 8.4 micromol/L) with low capacity (V(max,in vitro); 86.3 pmol/mg protein/min). These results show that the saturation of hepatic uptake by the carrier-mediated transport system could explain the nonlinear pharmacokinetics of TAK-044 in rats.

Systemic injection of FGF-2 stimulates endocortical bone modelling in SAMP6, a murine model of low turnover osteopenia.

The effects of systemically administered fibroblast growth factor-2 (FGF-2) at doses of 0.1 and 0.3 mg/kg/day for 7 days were investigated 5-week-old male SAMP6 mice, a model of low turnover osteopenia. The bone histomorphometry in the distal epiphyseal growth plate of the femur showed that 0.3 mg/kg/day of FGF-2 decreased the longitudinal growth rate and cartilage cell production rate and increased the growth plate width. Growth plate chondrocytes showed the features of defective endochondral ossification at the same dosage level. In the distal one third of the femur, the marrow trabecular area, endocortical mineral apposition rate and/or bone formation rate were increased in both the SAMP6 mice given 0.1 and 0.3 mg of FGF-2/kg/day. In this region, the endocortical osteoblasts were hypertrophied with some layers of overlying proliferated fibroblastic mesenchymal cells. The presence of small foci of bone formation within the layers of these mesenchymal cells indicates their osteogenic potential. On the other hand, the periosteal bone formation rate in the mid-shaft of the femur was depressed in the 0.3 mg/kg/day group. These results suggest that systemically administered FGF-2 may have the possibility to increase the peak bone mass in SAMP6 by stimulating the osteoprogenitor cells to proliferate and differentiate into osteoblasts and enhancing endocortical bone modelling. The higher dose of FGF-2, however, inhibited both endochondral and periosteal bone formation.

Effect of its demethylated metabolite on the pharmacokinetics of unchanged TAK-603, a new antirheumatic agent, in rats.

A factor in the dose-dependent pharmacokinetics of ethyl 4-(3, 4-dimethoxyphenyl)-6,7-dimethoxy-2-(1,2, 4-triazol-1-yl-methyl)quinoline-3-carboxylate (TAK-603) in rats was shown to be due to the inhibition of metabolic clearance of unchanged TAK-603 by its major metabolite, M-I, in other words, product inhibition. The effect of M-I on the metabolic clearance of TAK-603 was studied using rats continuously infused i.v. with this metabolite at rates of 5.3 and 16.0 mg/h/kg. The total body clearance of TAK-603 was decreased remarkably in M-I-infused rats, and the decline of total body clearance depended on the steady-state plasma concentrations of M-I. The effect of M-I generated from the dosed parent drug on the plasma concentration-time profile of TAK-603 was investigated using bile-cannulated rats after i.v. injection of 14C-labeled TAK-603 at doses of 1 and 15 mg/kg. Elimination rates of TAK-603 from rat plasma increased in the bile-cannulated rats in which systemic M-I levels were reduced by interrupting its enterohepatic circulation. To express, simultaneously, the relationships between TAK-603 and M-I in plasma concentration-time profiles, a kinetic model based on the product inhibition was developed for the bile-cannulated rats. A good agreement between calculated curves and the observed concentrations of both TAK-603 and M-I was found at 1 and 15 mg/kg, and the calculated curves were drawn using constant parameters for the two dosages. These results show that the product inhibition by M-I is one factor responsible for the dose-dependent pharmacokinetics of TAK-603 in rats.

Possible factor for nonlinear pharmacokinetics of TAK-603, a new antirheumatic agent, in rats.

A new antirheumatic, TAK-603, shows nonlinear pharmacokinetics in both animals and humans. To elucidate the mechanism of these nonlinear pharmacokinetics, in vivo and in vitro metabolism of 14C-labeled TAK-603 ([14C]TAK-603) was studied using rats as these resemble humans in their metabolic profiles. After intravenous injection of [14C]TAK-603 to rats at doses of 1, 5, and 15 mg kg(-1), the total body clearance of unchanged drug decreased significantly with increasing dose, whereas the apparent distribution volume did not alter remarkably. Thus, saturation in the elimination processes was considered to be a factor responsible for the nonlinear pharmacokinetics. The disappearance of unchanged drug from the circulation, however, followed a dose-dependent first-order process, indicating that the nonlinearity observed was not merely due to saturation of the elimination capacity. In vitro studies using rat liver microsomes showed that TAK-603 competitively inhibited CYP-catalysed nifedipine oxidation and also that the demethylated metabolite M-I, the major metabolite in rats and humans, competitively inhibited the oxidation of nifedipine. These results suggested that inhibition by M-I of the metabolism of the parent drug (i.e. product-inhibition) may be the most likely factor responsible for the nonlinear pharmacokinetics of TAK-603.

Aqueous humor dynamics in beagle dogs with caffeine-induced ocular hypertension.

In order to investigate the possible mechanisms for caffeine-induced ocular hypertension, the intraocular pressure (IOP) and the outflow through the trabecular meshwork were measured in beagle dog eyes after dosing with intravenous caffeine (30 mg/kg) alone or in combination with the topical beta-blocker befunolol [applied as 100 microliters of a 1% (w/v) solution] which inhibits aqueous humor formation in the ciliary body. Intravenous injections of caffeine significantly increased the IOP at 0.25 and 1 hr after a single dose. The ocular hypertension recovered within 2 hr following dosing. Over time, there were no differences in the outflow between the caffeine and control groups. The instillation of befunolol lowered outflow and produced ocular hypotension. The levels of the IOP and outflow in dogs treated with caffeine and befunolol in combination were almost the same as those in dogs treated with befunolol alone. Single-dose and combination-dose studies demonstrate that intravenous caffeine increases the IOP in normal beagle dogs possibly by increasing aqueous humor formation and not by the inhibition of aqueous humor drainage through the trabecular meshwork.

Frequency selectivity on aspirin-induced hearing loss in rats with auditory stimulus-induced conditioned suppression.

The conditioned suppression technique was employed to examine the acute effects of aspirin on auditory function in rats. Lever pressing behavior for water reinforcement was suppressed in the presence of an auditory stimulus that had been previously paired with electric shocks. A single intravenous injection of aspirin at a dose of 225 mg/kg caused an erroneous lever pressing response in the broad sound intensities of 2 kHz tone stimulus during the conditioned stimulus period. A statistically significant increase in the threshold for 2 kHz was found 1 to 72 hr after dosing but not for 4, 8 and 10 kHz. These results suggest that the hearing for low sound frequency in rats is vulnerable to the effects of aspirin. This paradigm in rats may be useful to further assess the different outer hair cells along the cochlear duct and provide an additional evidence for the aspirin ototoxicity research.

A characteristic of aspirin-induced hearing loss in auditory brainstem response of conscious rats.

The acute effects of aspirin on auditory functions were examined electrophysiologically in conscious rats with chronically implanted electrodes for auditory brainstem response (ABR) recording. A single intravenous injection of aspirin at a dose of 225 mg/kg caused a reduction in the amplitude of the ABR P1 wave evoked by a 2 kHz tone pip 1 and 24 hr after dosing at almost all sound intensity levels, while the P1 amplitude at 4 kHz was reduced mainly 1 hr after dosing, and the P1 amplitude at 8 kHz was not significantly affected at middle and high intensities even 1 hr after dosing. The audiogram obtained from the P1 amplitude showed a significant increase in the sound threshold 1 and 24 hr after dosing at 2 kHz, and 1 hr after dosing at 4 kHz, but not at 8 kHz. The peak latency of the P1 wave was also prolonged. Furthermore, reduction of the P2 and P4 wave amplitude and prolongation of the P1-P2 and P2-P4 interpeak latency were also observed at 2 kHz but not a 4 or 8 kHz. These results suggest that the rat auditory function for low frequency is vulnerable to the effects of aspirin. This paradigm, i.e., frequency selectivity, n rats may be useful to further assess the different outer hair cells along the cochlear duct and provide additional evidence for the mechanism(s) or site underlying aspirin ototoxicity.

Relationship between caffeine-induced ocular hypertension and ultrastructure changes of non-pigmented ciliary epithelial cells in rats.

The purpose of this study was to morphologically assess a possible mechanism for caffeine-induced ocular hypertension. Taking into consideration the relationship between the secretion of aqueous humor and the ultrastructure of the ciliary body, the time course of the morphological features in the ciliary epithelium when caffeine was administered intravenously to male Wistar rats was investigated by electron-microscopy. These morphological findings were also compared with the changes in the intraocular pressure (IOP). A significant increase in IOP was noted 15 min and 1 hr after a single dosing of caffeine alone. This change disappeared in all animals within 2 hr after dosing. The IOP in the animals receiving caffeine and the beta-blocker befunolol, which lowers the IOP by inhibiting aqueous humor secretion, decreased significantly from 15 min after dosing, and this change persisted 2 hr after dosing. In electron-microscopy 15 min and/or 1 hr after dosing with caffeine, a slight dilatation in the lateral intercellular spaces near the basement membrane of the non-pigmented ciliary epithelium was observed and the interdigitations between the non-pigmented epithelial cells were intact. Reversal of these changes was observed 2 hr after dosing. On the other hand, the lateral intercellular spaces between the non-pigmented epithelial cells were markedly dilated and the interdigitations were disorganized following dosing with caffeine alone and in combination with befunolol. These results described here indicate that the intravenous administration of caffeine causes ocular hypertension and also changes in the non-pigmented ciliary epithelium, suggesting an enhancement of aqueous humor transportation. This paradigm in the rat is considered to be useful to further assess caffeine-induced ocular hypertension and for use as an animal model in glaucoma research associated with an aqueous humor secretion.

Evaluation of Perkin's applanation tonometer and the normal range of intraocular pressure in anesthetized rats.

To assess the reliability of noninvasive measurement of intraocular pressure (IOP) in rats, a Perkin's applanation tonometer was calibrated against direct manometry. The normal values of IOP in male Wistar rats were then detected. The mean tonometer readings against the transducer IOP produced regression formula: y = -0.198 + 1.071 x (r2 = 0.987). The mean IOP with standard deviation in rats was 17.7 +/- 3.5 mm Hg (95% and 99% confidence intervals: 17.2 and 18.1 mm Hg, 17.0 and 18.3 mm Hg for the lower and upper limits of the normal rat IOP, respectively). The IOP could be measured accurately using Perkin's applanation tonometer in anesthetized rats each weighing 300 g and over. Measurement of IOP using this tonometer was considered to be valuable allowing, repeated use in rats because of its small size, portability and noninvasiveness.

Immunomodulating and articular protecting activities of a new anti-rheumatic drug, TAK-603.

We investigated the pharmacological activities of a newly synthesized anti-rheumatic drug, TAK-603. (1) In vivo: In adjuvant arthritic (AA) rats, TAK-603 inhibited the hind paw swelling and the body weight loss. The minimum effective dose was 3.13 mg/kg/day (p.o.). Histological and radiographic studies showed that TAK-603 suppressed the development of synovial lesions and joint and bone destruction. TAK-603 was also effective in AA rats when administered for the first 7 days after the adjuvant injection. It suppressed type IV allergy (25 mg/kg/day, p.o.) but had no effect on type III allergy. It had little effect in acute inflammation, analgesic and antipyretic models. These data suggest that TAK-603 acts on the immune system, especially on cellular immunity. (2) In vitro: TAK-603 suppressed the mitogen-induced proliferation of mouse lymphocytes and the ConA-induced IFN-gamma and IL-2 production by rat lymphocytes at 10(-7) to 10(-5) M. It also significantly inhibited the IL-1 induced extracellular matrix reduction in rabbit chondrocytes. It had no effects on prostaglandin E2 (PGE2) production in rat peritoneal cells. These data show that TAK-603 has the ability to suppress the immune system and protect cartilage from destruction. TAK-603 is expected to be a promising drug for rheumatoid arthritis.

Expression of ICAM-1 on glomeruli is associated with progression of diabetic nephropathy in a genetically obese diabetic rat, Wistar fatty.

We developed an animal model for non-insulin-dependent diabetes mellitus, a genetically obese rat strain, Wistar fatty. These rats show obesity-related features such as hyperinsulinemia and hyperlipemia, and only males develop diabetic features including hyperglycemia, glucoseuria and polyuria as they age. Histopathological study demonstrated a deposition of PAS-positive granules in the epithelial cells and a diffuse thickening of the mesangial area and moderate changes of the renal tubules. We found that ICAM-1 is expressed on the glomeruli of male Wistar fatty rats and the expression is associated with the development of nephropathy; it is weak at 5 weeks, becomes markedly strong at 15 weeks and progresses further at 29 weeks of age. We tried in vivo administration of monoclonal antibody, anti-ICAM-1 alone or together with anti-LFA-1 into male Wistar fatty rats during the period from 5 weeks to 17 weeks of age. The treatment, however, could not prevent the development of nephropathy. ICAM-1 expressed on the glomeruli of Wistar fatty rats seems not to play a key role in development of the nephropathy by mediating leukocyte infiltration. It will be a useful marker of the development of the disease.

Increase in femoral bone mass by ipriflavone alone and in combination with 1 alpha-hydroxyvitamin D3 in growing rats with skeletal unloading.

We assessed the possibility that ipriflavone treatment might result in bone restoration in immobilized rats. We also investigated the effect of combined treatment with ipriflavone and vitamin D3 on the bone. Male Sprague-Dawley rats, 6 weeks of age, were subjected to unilateral sciatic neurectomy. Three weeks after the operation, ipriflavone (100 mg/kg), 1 alpha-hydroxyvitamin D3 [1 alpha (OH)D3, 25 ng/kg], or both ipriflavone and 1 alpha (OH)D3 were orally administered every day for 12 or 24 weeks. After 12 weeks of treatment, only the group receiving combined treatment with ipriflavone and 1 alpha (OH)D3 showed increases in total femur calcium content (+16.4%, compared with the control). After 24 weeks, both animals treated with ipriflavone alone and those that had received the combination of ipriflavone and 1 alpha (OH)D3 showed significant increases in femur calcium content (+18.0% and +23.8%, respectively). In these treatment groups, X-ray analysis revealed an increase in bone mineral density over the entire length of the femur, and an increase in cortical diameter at the midshaft without affecting medullary width. Administration of 1 alpha (OH)D3 (25 ng/kg) alone had no effect. Body weight, femur length, and serum markers of calcium and bone metabolism were not affected in any group. We evaluated the relationship between ipriflavone and vitamin D3 in bone cells in a culture system using rat bone marrow stromal cells in which the cells subsequently form mineralized bone-like tissue. Continuous treatment with ipriflavone (10(-5) M) for 21 days resulted in an increase in osteocalcin secretion, and enhanced its response to 1 alpha, 25-dihydroxyvitamin D3 (10(-11) M-10(-8 M)). These findings indicate that ipriflavone treatment increases the femoral bone mass in immobilized rats. In addition, a low dose of 1 alpha (OH)D3, which did not induce hypercalcemia, in combination with ipriflavone, augmented the stimulatory effect of ipriflavone alone on the bone mass, possibly due to a direct effect of each agent on osteoblastic cells.

Dose-response relationships of cytotoxicity, PFC response and histology in the spleen in rats treated with alkylating agents.

Our previous study revealed the appropriate conditions for the plaque- forming cell (PFC) assay in rats. Using this assay in the present study, dose-response relationships of cytotoxicity, PFC response and histology in the spleen were evaluated in rats receiving alkylating agents. Rats were given a single intravenous administration of cyclophosphamide (CY) at a dose of 3, 10 or 30 mg/kg. Spleen weights and cellularity were decreased in the rats treated with 30 mg/kg. Suppressed PFC response wes observed in the rats receiving 10 mg/kg or more. In the rats treated with CY at 1, 3 or 10 mg/kg for 7 days, spleen weights and cellularity and PFC response were reduced at doses of 3 mg/kg or more. Treatment with the other alkylating agents, however, had a different consequence. Namely, in the rats treated with nitromin once or for 7 days, spleen weights and cellularity were decreased at a dose lower than that causing a reduction in the PFC response. In the rats treated with melphalan or chlorambucil, the weights and cellularity of the spleen tended to be decreased at a dose lower than that suppressing the PFC response. Histologically, in the case of CY, the marginal zone was narrow with cellular depletion in the rates receiving 3 mg/kg, whereas little change was seen in the periarteriolar lymphoid sheath (PALS). At a dose of 10 mg/kg, the marginal zone was markedly atrophied and slight atrophy of the PALS was seen. On the other hand, in the rats treated with nitromin, a dose-related decrease in the size of the spleen was seen without changes in the tissue architecture. Melphalan caused atrophy of both the marginal zone and the PALS at a dose suppressing PFC response. Regarding the red pulp, the extramedullary hematopoiesis disappeared with melphalan and nitromin, but not with CY. These results indicate that the decreases in weights and cellularity and histological changes in the spleen caused by the alkylating agents are detectable at the dose suppressing PFC response except for CY, which has a marked immunosuppressive action. Furthermore, the observed histological findings in the spleen were characteristic of each alkylating agent.

Potent ectopic bone-inducing activity of bone morphogenetic protein-4/7 heterodimer.

We have purified and characterized recombinant Xenopus bone morphogenetic proteins (xBMPs): homodimers of xBMP-4, 7 and heterodimers (xBMP-4/7) produced by a baculovirus expression system. Highly purified xBMPs had homogeneous NH2-termini predicted from a consensus motif, Arg-X-X-Arg, while they possessed diverse sugar chains. Implantation of xBMPs together with pure collagen carrier in rats induced new bone formation in a dose-dependent manner. The xBMP-4/7 heterodimer showed the strongest activity, with an effective dose of 1-30 micrograms, while more than 10 micrograms of xBMP-4 or 7 homodimer was required for a significant effect. Histological examination revealed that xBMP-4/7 implants showed intramembranous ossification without chondrogenesis. In primary cultures of rat bone marrow stromal cells, xBMP-4/7 induced alkaline phosphatase 3-fold more strongly than xBMP-7 and 20-fold more than xBMP-4. These results suggest that the heterodimeric form of BMP would generate the strongest signal triggering osteogenic differentiation of osteoprogenitor cells in adult tissues.

Effects of basic fibroblast growth factor (bFGF) on bone formation in growing rats.

The effects of basic fibroblasts growth factor (bFGF) administered intravenously at dosages of 0.1 and 0.3 mg/kg per day for 7 days to growing rats are reported. Static and dynamic histomorphometry techniques were applied to the microradiographs and undecalcified ground sections of the proximal tibiae and tibial shafts. The bone histomorphometric analyses in the proximal tibia revealed that 0.1 mg/kg per day of bFGF increased longitudinal growth rate, cartilage cell production rate, and metaphyseal bone area. In the tibial shaft, the endocortical mineral apposition and bone formation rates, total bone area, total osteoid area, and medullary bone area were increased, but the periosteal mineral apposition and bone formation rates were depressed. Two weeks after the cessation of treatment, the increased osteoid bone on the endocortical surface and in the marrow cavity was completely calcified, and the total mineralized area in the tibial shaft was significantly increased. The rats given 0.3 mg of bFGF/kg per day showed retarded weight gain, defective calcification at the growth plate metaphyseal junction, and on the endocortical surface. The growth plate width was increased, and the longitudinal growth rate, cartilage cell production rate, endocortical labeled surface, and bone formation rate were decreased. Two weeks after the cessation of treatment, these changes were almost reversed, and the longitudinal growth rate and cartilage cell production rate were increased as rebound phenomena. These results suggest that a low dose (0.1 mg/kg per day) of bFGF stimulates endosteal and endochondral bone formation and depresses periosteal bone formation in growing rats.

Pharmacological modulation of immediate and late airway response and leukocyte infiltration in the guinea pig.

We established an experimental model of late asthmatic response (LAR) using conscious guinea pigs actively sensitized by antigen aerosol inhalation. In actively sensitized guinea pigs, antigen challenge by aerosol inhalation caused an immediate increase in specific airway resistance (SRaw) (immediate airway response; IAR) followed by a LAR which occurred 4 to 8 hr after antigen challenge. SRaw in the challenged animals was still increased 23 hr after antigen challenge. Examination of bronchoalveolar lavage (BAL) fluid and histology of the lungs revealed increases in eosinophils and neutrophils during LAR. The beta-2 agonist salbutamol inhibited only IAR and not LAR. Dexamethasone inhibited LAR but not IAR. A low dose of theophylline had little effect on both IAR and LAR. A novel thromboxane A2 (TXA2) receptor antagonist, AA-2414, orally administered before antigen challenge dose-dependently inhibited both IAR and LAR, and oral administration of AA-2414 after the IAR inhibited LAR. Also, thromboxane synthetase inhibitors, CV-4151 and OKY-046, reduced both IAR and LAR. Salbutamol significantly reduced the increase in neutrophils in BAL fluid, and dexamethasone significantly reduced the increase in eosinophils and neutrophils in BAL fluid. Theophylline also reduced the increase in eosinophils in BAL fluid. However, AA-2414 did not inhibit the accumulation of these inflammatory cells in BAL fluid or the airway tissues. These results suggest that asthmatic responses in guinea pigs are similar to those in asthmatic subjects and that TXA2 plays an important role in both IAR and LAR but not in inflammatory cell infiltration in this model of allergic asthma.

Effect of ipriflavone on expression of markers characteristic of the osteoblast phenotype in rat bone marrow stromal cell culture.

The effects of ipriflavone on cellular proliferation and differentiation of osteoblasts were investigated using stromal cells isolated from the femoral bone marrow of young rats. To induce the formation of mineralized bone-like tissue in vitro, the cells were cultured in the presence of beta-glycerophosphate and dexamethasone. Ipriflavone was added when subculturing was started. After 14 days of culturing with ipriflavone (10(-7)-10(-5) M), increases in both the alkaline phosphatase activity and the hydroxyproline content per culture dish and a slight decrease in the saturated cell density were observed. Furthermore, continuous treatment with ipriflavone for 14-33 days resulted in an increase in the area of bone-like mineralized tissue accompanied by an increase in the secretion of osteocalcin. When culture medium lacking dexamethasone was used, rat bone marrow stromal cells neither differentiated into osteoblasts nor formed bone-like tissue, and under these conditions, ipriflavone had no effect on the proliferation or the phenotypic expression of the cells. These results suggest that ipriflavone directly stimulates markers of the osteoblast phenotype at a certain stage in bone formation without affecting undifferentiated cells that have not been committed to the osteogenic lineage.

Upregulation of fibroblast growth factor-receptor messenger RNA expression in rat brain following transient forebrain ischemia.

Recently, we demonstrated that transient forebrain ischemia in rats leads to an early and strong induction of basic fibroblast growth factor (bFGF) synthesis in astrocytes in the injured brain regions. In this study, in order to clarify the targets of such raised endogenous bFGF levels, the messenger RNA (mRNA) expression of its receptors (flg and bek) in the hippocampus following transient forebrain ischemia induced by four-vessel occlusion for 20 min was investigated using an in situ hybridization technique. Transient forebrain ischemia induced an increase in the number of flg mRNA-positive cells from an early stage (24 h after ischemia) in the hippocampal CA1 subfield where delayed neuronal death occurred later (48-72 h after ischemia). This increase became more marked with the progression of neuronal death and was still evident in the same area 30 days later. The time course of the appearance and distribution pattern of flg mRNA-positive cells in the CA1 subfield were quite similar to those of bFGF mRNA-positive cells. On the other hand, in situ hybridization for bek mRNA showed only slight and transient (observed 72 h and 5 days after ischemia) increases in the number of mRNA-positive cells in the CA1 subfield following ischemia. The use of in situ hybridization and glial fibrillary acidic protein immunohistochemistry in combination demonstrated that the cells in the CA1 subfield that exhibited ischemia-induced flg or bek mRNA expression were astrocytes. These data indicate that transient forebrain ischemia induces upregulation of fibroblast growth factor-receptor expression, accompanied by increased bFGF expression in astrocytes, and suggest that the increased astrocytic bFGF levels in injured brain regions act on the astrocytes via autocrine systems and are involved in the development and maintenance of astrocytosis.

In vivo stimulation of endosteal bone formation by basic fibroblast growth factor in rats.

Intravenous administration of human basic fibroblast growth factor (bFGF) for 2 weeks stimulated osteoblast proliferation and new bone formation in various skeletal bones in young and aged rats at dosage levels of 0.1 mg/kg/day and greater. Morphometry of the soft X-ray radiograms of cross sections of the tibia indicated about a 20% increase in the calcified bone area of the diaphysis at 0.1 mg/kg/day. The Ca and hydroxyproline contents showed statistically significant increases at this dosage. The new bone formation was found only on the endosteal side, and no periosteal bone formation was found. Similar systemic osteogenic potential was seen after intravenous administration of other growth factors of the FGF family, human acidic FGF and human heparin-binding secretory transforming protein-1. The above results suggest a potential therapeutic role for these growth factors in bone-loss diseases such as osteoporosis.

Biochemical analysis of the bone of SHC rats with spontaneous hypercholesterolemia and renal dysfunction.

Spontaneously hypercholesterolemic (SHC) rats exhibit severe abnormalities in renal function and bone metabolism at old ages, in addition to hypercholesterolemia. SHC rats were also found to show endocrine abnormalities such as hyperthyroidism from young ages. In this study, biochemical and microdensitometric analyses were carried out using femurs to characterize further the abnormality in bone metabolism: whether biochemical markers of the bone may be affected by these abnormalities. At 6 weeks of age, the ashed weight and calcium content of the dried femurs were slightly lower in SHC rats than in age-matched Sprague-Dawley (SD) rats. None of the markers of microdensitometric analysis was changed. At 24 weeks of age, the ashed weight of dried femurs and the density of the marrow region of femurs were lower in the SHC rats. The results indicate that SHC rats exhibit severe abnormality in bone metabolism leading to biochemical changes in the bone at old ages whereas changes in bone markers were minimal at young ages before the onset of severe renal dysfunction.