Effect of purified saponin mixture from Astragalus corniculatus on enzyme- and non-enzyme-induced lipid peroxidation in liver microsomes from spontaneously hypertensive rats and normotensive rats.

The aim of the following study was to evaluate the effect of a purified saponin mixture (PSM), isolated from Astragalus corniculatus Bieb. (Fabaceae), on enzyme-induced and non-enzyme-induced lipid peroxidation (LPO), in liver microsomes from spontaneously hypertensive rats (SHRs) - strain Okamoto Aoki, as compared to normotensive Wistar rats (NTRs). The enzyme-induced lipid peroxidation was performed by incubating rat liver microsomes with carbonetetrachloride (CCl(4)) in the presence of NADPH. In nonenzyme-induced LPO, the microsomes were incubated with a solution of iron sulphate and ascorbinic acid (Fe(2+)/AA). The effect of PSM (196.5 microg/ml) was assessed at 20 minutes' incubation time. MDA, a product of LPO, was measured spectrophotometrically. The results of our study showed that the initial MDA quantity in SHRs was significantly higher, than in NTRs. The incubation of the microsomes from both strains with PSM (196.5 microg/ml), resulted in significant reduction of MDA level, by 25% in SHRs. In NTRs, the formation of MDA was unchanged. In enzyme-induced LPO model, PSM significantly decreased the formation of MDA, by 55% in NTRs and by 35% in SHRs, compared to the respective control groups. In the model of non-enzyme induced LPO, PSM significantly decreased the formation of MDA by 95% in NTRs and practically restored it to the control level. The MDA quantity in SHR's microsomes was reduced by 25%. According to the results of this experiment we could conclude that PSM, isolated from Astragalus corniculatus, shows antioxidant activity both in SHRs and NTRs and the effect in NTRs is more pronounced.

In vitro study of lovastatin interactions with amiodarone and with carbon tetrachloride in isolated rat hepatocytes.

AIM: To investigate the interactions at a metabolic level between lovastatin, amiodarone and carbon tetrachloride in isolated rat hepatocytes. METHODS: For cell isolation two-step collagenase liver perfusion was performed. Lovastatin was administered alone in increasing concentrations (1 mumol/L, 3 mumol/L, 5 mumol/L and 10 mumol/L) and in combination with CCl(4) (86 mumol/L). The cells were also pretreated with 14 mumol/L amiodarone and then the other two compounds were added. RESULTS: Lovastatin promoted concentration-dependent significant toxicity estimated by decrease in cell viability and GSH level by 45% and 84%, respectively. LDH-activity increased by 114% and TBARS content by 90%. CCl(4)induced the expected severe damage on the examined parameters. CCl(4) induced toxicity was attenuated after lovastatin pretreatment, which was expressed in less increased values of LDH activity and TBARS levels, as well as in less decreased cell viability and GSH concentrations. However, the pretreatment of hepatocytes with amiodarone abolished the protective effect of lovastatin. CONCLUSION: We suggest that the observed cytoprotective effect was due to interactions between lovastatin, CCl(4) and amiodarone at a metabolic level.

Effects of nifedipine on behavioral and biochemical parameters in rats after multiple morphine administration.

Numerous studies indicate that opioid tolerance involves a disruption in Ca2+ homeostasis. In vivo studies have indicated the involvement of dihydropyridine-sensitive (L-type) voltage-gated channels in morphine abuse. In this study, the effect of multiple administration of the dihydropyridine calcium channel blocker nifedipine (5 mg/kg/twice daily), given in combination with morphine, on the signs of morphine withdrawal and some biochemical parameters were assessed. Multiple morphine administration in increasing doses (from 5 to 40 mg/kg for 7 days) and consequent withdrawal after 18 h, induced writhing, squealing, diarrhea, teeth chattering, eyelid ptosis and wet-dog type shaking. Coadministration of nifedipine prevented the squealing, diarrhea and teeth chattering. On a biochemical level, the activity of brain nitric oxide synthase (NOS) and the quantity of cytochrome P450 in rat brain and liver were measured. Nifedipine treatment decreased the brain nNOS activity, induced by multiple administration of morphine. The quantity of liver cytochrome P450, after multiple coadministration of morphine and nifedipine, was also increased. The quantity of brain cytochrome P450 was not significantly changed by morphine and nifedipine alone or in combination. The results of our study suggest that nifedipine influences the effects of morphine both at a pharmacokinetic and a pharmacodynamic level.

Effects of two newly synthesized 4-hydroxycoumarin derivatives (4-OHC) on isolated rat hepatocytes.

To clarify the hepatotoxicity of two newly synthesized derivatives of 4-hydroxycoumarin (OX and AC) with proven anticoagulant activity in comparison with warfarin, we investigated freshly isolated rat hepatocytes. Hepatocyte damage after incubation with OX, AC and warfarin at a final concentration of 1 x 10(-8) M to 1 x 10(-3) M was assessed by measuring cell viability, lactatdehydrogenase (LDH) activity and glutathione (GSH) levels. The results of cell viability assessment showed that warfarin had the highest toxicity, followed by OX and AC. LDH activity of the tested compounds was mostly increased by warfarin. According to the average effective concentration of the compounds on this parameter, warfarin possessed the most significant toxic effect (EC50 = 1 x 10(-7) M), followed by AC (EC50 = 9.7 x 10(-5) M) and OX (EC50 = 5.0 x 10(-4) M). The observed cytotoxic effects were most pronounced in the highest concentration 1 x 10(-3) M as follows: warfarin, AC and OX. The differences in the effects of OX and AC may be explained by the differences in the electronic structure of the novel compounds, as assessed by molecular modeling.

Development of model aqueous ophthalmic solution of indomethacin.

A new model aqueous solution of indomethacin was developed on the basis of Pluronic F68 (15%) and F127 (10%). They showed some practical advantages over the models prepared with polyols and polysorbate 80, which were used for comparison. It was found that both Pluronics acted very similarly and were more effective as solubilizers, created an appropriate viscosity, and formed reversible gels at higher temperatures, ensured the indomethacin chemical stability and prolonged in vitro drug diffusion, and showed high physiological tolerance on rabbit eyes. Moreover, indomethacin stability and solution viscosity in the presence of Pluronics did not change after heat sterilization (i.e., the samples can bear heat sterilization).

Synthesis, toxicity and immunomodulating activity of Co(II), Ni(II), Cu(II) and Zn(II) complexes of L(-)-2,3,5,6-tetrahydro-6-phenylimidazo[2,1-b]thiazole (levamisole).

Co(II), Ni(II), Cu(II) and Zn(II) complexes of levamisole (LMS) were prepared and characterized by elemental analyses, IR spectroscopy, 1H and 13C NMR and mass spectrometry. The following general formula was derived: M(LMS)2Cl2, where M = Co, Ni, Cu, Zn. It was established that LMS behaved as a monodentate ligand and the coordination was accomplished through the N-7 atom. The toxicity and the immunomodulating activity of the complexes on mice and rats in comparison with uncomplexed LMS was assayed. The metals in the complexes exerted different changes in the toxicity of LMS. The complex containing Zn(II) was less toxic and manifested higher immunomodulating activity than LMS.

Biochemical and morphological studies on the effects of anthocyans and vitamin E on carbon tetrachloride induced liver injury.

The effects of the natural antioxidants-anthocyans and vitamin E (in a solubilized pharmaceutical form) on carbon tetrachloride-induced liver injury in rats are studied. The changes in the activity of serum transaminases (ALAT and ASAT), the content of the reduced glutathione and cytochrome P-450 as well as the intensity of the processes of lipid peroxidation are assessed. The anthocyans exert a protective effect comparable to that of vitamin E on liver cells. The favorable effects of the combination of the antioxidants on the content of the reduced glutathione and on the processes of lipid peroxidation are more intensely expressed. The morphological changes occurring in hepatocytes correlate with the results of the biochemical studies. It is evident that both substances have a marked hepatoprotective activity.

Influence of the combined chemotherapeutic drug tuboprim on drug metabolism.

Tuboprim (Pharmachim, Bulgaria) is a combined synergistic chemotherapeutic drug, containing rifampicin (Tubocin-Pharmachim) (TB) and trimetoprim (TM). In experiments on rats and mice the influence of single and repeated (4 days) doses of Tuboprim and of the corresponding doses of TB and TM on some drug metabolizing enzyme systems and other factors of drug metabolism was studied. The following indices were investigated: hexobarbital sleeping time (HBST), activities of hexobarbital oxidaze (HBO), aniline hydroxylase (AH), ethylmorphine-N-demethylase (EMND), uridindiphosphoglucuronyl-transferase (UDPGT), NADPH-cytochrome-C reductase and the cytochrome P-450, cytochrome b5 and microsomal protein contents. A single dose of TB (100 mg/kg in rats and 80 mg/kg in mice) inhibited HBO, EMND and AH; TM (30 mg/kg in rats and 20 mg/kg in mice) inhibited HBO and EMND, whereas Tuboprim inhibited EMND only. Repeated (4 days) treatment with TB provoked an induction of HBO, AH, and EMND accompanied by an increase of NADPH-Cyt-C reductase and cytochrome P-450, hem and microsomal protein content. Trimetoprim stimulated EMND only. The combined drug Tuboprim also produced an enzyme induction, but to a considerably less degree than did TB alone. UDPGT activity was not significantly changed.