Journal of pharmacobio-dynamics最新文献

We studied the effect of feeding ursodeoxycholylcysteic acid, the cysteic acid conjugated analog of ursodeoxycholyltaurine, on serum and liver cholesterol levels and on intestinal absorption of cholesterol and bile salts in hamsters. Addition of ursodeoxycholylcysteic acid to the cholesterol-enriched diet reduced the elevation of serum and liver cholesterol levels caused by feeding cholesterol. However, supplementation with ursodeoxycholylcysteic acid to the standard diet did not show any significant change in serum and liver cholesterol levels. Administration of ursodeoxycholylcysteic acid caused a decrease in dietary cholesterol absorption but did not interfere with the ileal transport of endogenous bile salts. Hence the hypocholesterolemic activity of dietary ursodeoxycholylcysteic acid is thought to be the effect on intestinal absorption of cholesterol but not to be the interruption of the enterohepatic circulation of bile salts.

The chromosomal aberration test using a Chinese hamster lung cell line (CHL) was carried out on 19 aporphine alkaloids including apomorphine with and without rat liver homogenates (S9) mix. Eighteen of 19 alkaloids tested induced chromosomal aberration in the presence or absence of S9 mix. Among the alkaloids tested, anolobine, liriodenine and 4,5-dioxodehydrocrebanine induced chromosomal aberrations at relatively low concentrations and as low as 2.5, 5 and 3.13 micrograms/ml, respectively. Dicentrine, anolobine and 4,5-dioxodehydrocrebanine induced chromosomal aberrations with high frequencies. Apomorphine induced 10% aberrant cells at 12.5 micrograms/ml in the direct method and 12% at 100 micrograms/ml with S9 mix in the S9 method. Liriodenine which was the most potent mutagen for TA100 with S9 mix and roemerine which was the most potent for TA98 with S9 mix in Ames test were also clastogenic with and without S9 mix.

In order to clarify the mechanism of intestinal absorption of an antibiotic, fosfomycin (FOM), the uptakes of FOM by rabbit and human small intestinal brush-border membrane vesicles (BBMV) were studied. The initial uptake of FOM by BBMV at 15 s was saturable at a higher concentration of FOM. The kinetic parameters at 37 degrees C of the saturable uptake expressed by the Michaelis-Menten equation were Kt = 5.17 mM and Jmax = 3.88 nmol/15 s/mg protein for rabbits, and Kt = 4.03 mM and Jmax = 1.90 nmol/15 s/mg protein for humans. The most efficient uptake was observed in the presence of both inward-directed Na(+)- and H(+)-gradients in both mammals. The uptake of FOM was inhibited by inorganic phosphate, FOM glycol which is a degradation product of FOM in the gastric juice and specific inhibitors of phosphate transport such as arsenate and phosphonoacetic acid. These findings confirmed that FOM absorption from rabbit and human small intestines is associated with the phosphate transport system. These transport phenomena of FOM are in close agreement with those obtained previously in rat BBMV studies. Judging from the results obtained for three mammalian species, rat, rabbit and human, it was concluded that carrier-mediated transport via the phosphate transport system is a very important pathway of intestinal absorption of FOM.

Release of endogenous taurine by electrical stimulation of slices of the hippocampus, cerebral cortex, cerebellum and medulla oblongata of the rat was studied and compared with that of alanine and/or gamma-aminobutyric acid (GABA). Electrical stimulation caused a calcium-dependent release of taurine from slices of the hippocampus, cerebral cortex and cerebellum but not from slices of the medulla oblongata. The stimulus-evoked release of taurine in the hippocampus was rapid in onset and declined to baseline fast, which was essentially similar to the time course pattern of the stimulus-evoked release of GABA. In addition, there were distinct regional differences in the relative amounts of taurine released. Electrical stimulation did not release alanine from any regions examined. These results support the hypothesis that taurine plays a neurotransmitter role in the hippocampus, cerebral cortex and cerebellum of the rat.

We have shown previously that recombinant human interleukin 1(IL-1) and interleukin 6 (IL-6) inhibited the proliferation of a mouse myeloid leukemic cell line (M1), and that IL-6 induced differentiation of the cells into macrophage-like cells and that IL-1 augmented this differentiation. Using this model we investigated the action mechanisms of IL-1 and IL-6. IL-6, but not IL-1, stimulated prostaglandin E2 (PGE2) production. The differentiative effect of IL-6 however, was not suppressed by indomethacin, although PGE2 induction by IL-6 was completely inhibited. Exogenously added PGE2 neither augmented the differentiative effect of IL-6 nor induced differentiation in combination with IL-1. Therefore, stimulation of PGE2 production did not appear to be essential for differentiative effects of these cytokines. Dibutyryl cAMP, 8-Br-cAMP and two adenylate cyclase-activating reagents, cholera toxin (CT) and forskolin (FK), all exhibited the similar augmenting effects as IL-1. These reagents augmented M1 cell differentiation by IL-6, and they did not induce differentiation in combination with IL-1. cAMP derivatives, CT, FK, IL-1 and IL-6 all inhibited the proliferation of M1 cells. CT and FK increased the intracellular cAMP levels. However, neither IL-1 nor IL-6 increased the cAMP levels. In contrast to the cAMP derivatives and reagents that activate adenylate cyclase activity, phorbol 12-myristate 13-acetate (PMA) and calcium ionophore neither induced nor augmented the differentiation in combination with either IL-1 or IL-6. Intracellular Ca2+ concentration was not altered by IL-1 or IL-6 suggesting that Ca2+/Calmodulin kinase and protein kinase C activation are not involved in this signal transduction pathway. Therefore, the present study suggests that IL-1 exhibits an effect similar to that of cAMP without affecting intracellular cAMP level.

The effect of glutathione depletor diethylmaleate on rat hepatic glutathione S-transferase and glutathione peroxidase was studied in vivo and in vitro. When diethylmaleate (600 mg/kg) was given i.p. to rats, liver glutathione was depleted within 2 h and recovered to the control level 5 h after diethylmaleate treatment. Both glutathione S-transferase and peroxidase activities in microsomes, not in cytosol, were markedly increased during glutathione depletion and only glutathione S-transferase activity remained at high levels after recovery of the glutathione content. The increase in microsomal glutathione S-transferase and peroxidase activities with concomitant exhaustion of glutathione was also observed by perfusion of the isolated liver with diethylmaleate (10 mM). When liver microsomes were incubated with diethylmaleate in vitro at 37 degrees C, glutathione S-transferase, but not peroxidase, activity was increased; the increase was not reversed by dithiothreitol. These results indicate that diethylmaleate activates microsomal glutathione S-transferase by direct reaction to the enzyme during glutathione depletion and suggest that glutathione S-transferase activity and glutathione peroxidase activity in the microsomal enzyme may be differently regulated.

Urinary excretion of enzymes by rats was assessed after glutathione (GSH) was depleted by treatment with a mixture of the GSH depletors D,L-buthionine-S,R-sulfoximine (BSO) and diethylmaleate (DEM). Renal GSH was low 2 h after treatment and later returned to the control level. The urinary excretion of gamma-glutamyltranspeptidase (gamma-GTP) and N-acetyl-beta-D-glucosaminidase (NAG) remained high for at least 3 d after the injection of BSO (100 mg/kg) and DEM (0.5 ml/kg), with no effect on the blood urea nitrogen level. N,N'-Dimethylthiourea (DMTU), a scavenger of oxygen free radicals, inhibited this increase in the urinary excretion of gamma-GTP. DMTU also inhibited the increase in cisplatin-induced NAG excretion caused by the GSH depletors. These results suggested that the urinary excretion of these enzymes is an index of renal tubular injury caused by short-term depletion of renal GSH, and that the generation of free radicals may be involved in renal tubular injury during GSH depletion or caused by cisplatin together with GSH depletors.

A sensitive enzyme-linked immunosorbent assay (ELISA) for rat interleukin 8/cytokine-induced neutrophil chemoattractant (CINC) has been established by using biotin-conjugated anti-CINC rabbit IgG. The biotin-streptavidin sandwich ELISA detected CINC at concentrations from 3 pg/ml up to 30 ng/ml. The concentration of CINC in the pouch fluid (exudate) of rat carrageenin-induced inflammation was measured by the ELISA. After a time lag of about 2 h, neutrophils steadily accumulated in the carrageenin/air-pouch until 8 h. Similarly, the CINC level of exudate increased after about a 2-h lag, and reached a maximum (134 ng/ml) at 8 h, and thereafter decreased to a negligible concentration at 24 h after carrageenin injection. In association with the rise in CINC level, the concentration of exudate 96-kDa gelatinase corresponding to neutrophil gelatinase/type IV collagenase increased with time. The results suggest that CINC contributes, at least in part, to the neutrophil migration into the inflammatory lesion of the carrageenin-induced inflammation in rats.

The aim of the study was to compare two methods classically used in rats to determine the fractional catabolic rate (FCR) of labeled high or low density lipoproteins: constant infusion and single pulse. The FC of [14C]-sucrose HDL (High density lipoprotein) was studied. For the short term experiment (8 hours), both methods gave similar FCR determined 8 hours after HDL constant infusion (9.4%.h-1 +/- 0.6) or single pulse (8.5%.h-1 +/- 0.4), values significantly higher than those measured 24 hr after the single pulse (6.2%.h-1 +/- 0.3). The identification and simulation of the model representing HDL movements between an intravascular and extravascular pool, after single pulse and constant infusion methods, demonstrated that FCR of lipoproteins cannot be precisely measured with techniques involving excessively short observation periods.

The enantioselective oral bioavailability of propranolol (PL) from 0-isovaleryl-PL was determined and compared with parent PL in beagle dogs. The bioavailability of the individual enantiomer from the prodrug increased about 2 fold. The AUC ratio between the S(-)- and R(+)-isomer posed at 0.89 which was statistically not different from that obtained after administration of PL alone. These features indicate that 0-isovaleryl-PL promises to be a potential prodrug of PL from the pharmacokinetic and pharmacodynamic point of view.