Sex-dependent differences in the effects of portacaval anastomosis on hepatic monooxygenases in rats.

Previous work revealed that portacaval anastomosis (PCA) in rats results in hepatic atrophy and marked decreases in components of the microsomal monooxygenase system such as cytochrome P-450. In the present study, the effects of PCA on hepatic monooxygenase activity were studied in more detail. We report that PCA, in general, produces effects resembling those of castration. Thus, in male rats, PCA depressed the activity of highly sex-dependent enzymes such as ethylmorphine and aminopyrine demethylases. Similar effects were produced by castration, and the combination of PCA and castration produced the same effect as either treatment alone. In male rats, non-sex-dependent enzymes such as aniline hydroxylase and NADPH-cytochrome c reductase were unaffected by either PCA or castration. By contrast, in female rats, neither PCA nor castration significantly affected microsomal monooxygenase activities. In male rats, PCA was accompanied by a 75% reduction in serum testosterone levels and a 6-fold increase in total estrogen levels. We conclude that these effects of PCA in male rats were due, in large measure, to a demasculinizing effect.

Immunochemical study on the pathway of electron flow in reduced nicotinamide adenine dinucleotide-dependent microsomal lipid peroxidation.

NADH could support the lipid peroxidation of rat liver microsomes in the presence of ferric ions chelated by ADP(ADP-Fe). The reaction had a broad pH optimum (pH 5.8--7.4) and was more active in the acidic pH range. Antibodies to NADH-cytochrome b5 reductase [EC 1.6.2.2] and cytochrome b5 inhibited NADH-dependent lipid peroxidation in the presence of ADP-Fe, whereas the antibody against NADPH-cytochrome c reductase [EC 1.6.2.4] showed no inhibition. These oberservations suggest that the electron from NADH was supplied to the lipid peroxidation reaction via NADH-cytochrome b5 reductase and cytochrome b5. On the other hand, NADPH-supported lipid peroxidation was strongly inhibited by the antibody against NADPH-cytochrome c reductase, confirming the participation of this this flavoprotein in the NADPH-dependent reaction. In the presence of both ADP-Fe and ferric ions chelated by EDTA(EDTA-Fe), NADH-dependent lipid peroxidation was highly stimulated up to the level of the NADPH-dependent reaction. In this case, the antibody against cytochrome b5 could not inhibit the reaction, while the antibody against NADH-cytochrome b5 reductase did inhibit it, suggesting the direct transfer of electrons from NADH-cytochrome b5 reductase to EDTA-Fe complex.

Alterations in hepatic and renal levels of glutathione and activities of glutathione S-transferase from rats treated with cis-dichlorodiammineplatinum-II.

Adult female rats were treated intraperitoneally with 8 mg/kg of cis-dichlorodiammineplatinum(II). At various times after treatment 1, 3, 5, 8, 12 days replicate animals were killed and liver and kidney cytosols examined for activity of glutathione-dependent transferase activities and levels of glutathione. Hepatic levels of glutathione were depressed by 13-28% at 1, 3, 5 days after dosing. Renal levels of glutathione were increased by 3-5 fold at 8 and 12 days after drug administration. Renal levels of glutathione were decreased at nearly all times studied with a nadir at 5 days. Activity of glutathione s-acryl transferase was increased and S-epoxidetransferase was decreased at 5, 8, 12 days after dosing. When cisplatinum was added to incubation mixtures in vitro, no changes in enzyme activities were observed. When cisplatin and reduced glutathione were determined chromatographically in tissue cytosols from treated rats, 30% of the recovered platinum was associated with glutathione. In tissue cytosols, greater than 95% of the total platinum content was retained in the supernatant when protein was precipitated with trichloroacetic acid, while only 3-5% of the protein was retained.

Sex differences in the uptake and retention of imipramine and desmethylimipramine in the rat lung.

14C-Imipramine was administered to male and female Sprague-Dawley rats and animals were sacrificed at 4, 8, 12, and 20 hours later. At all time points, total radioactivity in female lung was several-fold higher than in males. In addition, female lungs had a higher concentration of desmethylimipramine (DMI) as compared to imipramine than did male rat lungs. This was reflected by a higher conversion of imipramine to DMI by hepatic and pulmonary microsomes from female rats. Finally male rats cleared both imipramine and DMI from their lungs at a slower rate than did female rats.

Interaction of the oncolytic drug, 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea with the mixed-function oxidase system in rats.

Effects of 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU) on the hepatic mixed-function oxidase system in male rats were studied both in vivo and in vitro. A single dose of CCNU (40 mg/kg) caused a significant reduction in hepatic mixed-function oxidase activities within 3 days after administration. The depression was prolonged for cytochrome P-450, total haem and the metabolism of several type I substrates lasting up to 10 weeks after a single dose. By contrast, aniline hydroxylase, cytochrome b5 and NADPH-cytochrome c reductase activities returned to near control levels after week two. Microsomal enzymes in the kidneys of treated animals however, were unaltered. Serum glutamic pyruvic and glutamic oxaloacetic transaminase and bilirubin levels, indicators of hepatotoxicity, were greatly elevated 3 days after CCNU treatment. These parameters fell rapidly but were still above control levels to the end of the 10-week study. When added in vitro, CCNU reduced apparent cytochrome P-450 content and the metabolism of type I substrates in microsomes from untreated, phenobarbital (PB) and 3-methylcholanthrene (3-MC)-pretreated rats. Total haem and NADPH-cytochrome c reductase were not affected whereas aniline hydroxylase activity was activated. CCNU interacted with hepatic microsomes to produce a type I difference spectrum.

Inhibition of mitochondrial respiration by sodium nitroprusside and the mechanism of cyanide liberation.

The influence of sodium nitroprusside (SNP) on mitochondrial respiration was examined in rat liver mitochondria. The addition of SNP 1 mmol litre-1 during state 3 respiration inhibited the oxygen uptake by 63.4%. A mixture of SNP 1 mmol litre-1 and glutathione (GSH) 1 mmol litre-1 inhibited the oxygen uptake more markedly (by 75.9%). The cyanide concentrations were 0.01 mmol litre-1 with SNP alone and 0.15 mmol litre-1 with the mixture of SNP and GSH. Cyanide production from SNP in the presence of various reducing agents was studied in potassium phosphate 0.1 mol litre-1 buffer solution (pH 7.4) incubated at 37 degrees C. Cyanide was liberated markedly from SNP in the presence of GSH or ascorbate. Less cyanide was produced in the presence of NADH or NADPH. The rate of production of cyanide was dependent entirely upon the concentration of each reducing agent added. No cyanide was liberated when sodium dithionite or the oxidized forms of GSH, NAD or NADP were used. It was concluded that SNP is degradated to cyanide by a hydrogen donor and that the cyanide liberated in this manner inhibits the cytochrome oxidase activity of mitochondria in vivo.

The in vitro metabolism of halothane (2-bromo-2-chloro-1,1,1-trifluoroethane) by hepatic microsomal cytochrome P-450.

Incubation of halothane with rabbit liver microsomes in the presence of NADPH and oxygen resulted in the formation of trifluoroacetic acid (TFAA). No TFAA was detected in the absence of either NADPH or oxygen. TFAA also was found when a 9000 x g supernatant fraction (with NADPH and oxygen) was used instead of the microsomal fraction. The 105,000 x g supernatant fraction (with NADPH and oxygen), however, did not produce detectable levels of TFAA. Phenobarbital pretreatment of the animals resulted ina significant increase in both the formation of TFAA and the cytochrome P-450 content of microsomes. A good correlation was found between formation of TFAA and microsomal cytochrome P-450 levels. The amount of TFAA formed in hepatic microsomes was significantly inhibited by carbon monoxide (CO), SKF 525-A (2-diethylaminoethyl-2,2,-diphenylvalerate HCl) and p-chloromercuribenzoic acid. On the other hand, TFAA was formed when NADH was used as an electron donor instead of NADPH. In conclusion, these results clearly demonstrate the metabolism of halothane by the hepatic microsomal mixed-function oxidase system.

Stimulation of microsomal drug oxidation in liver and kidney of rats treated with the oncolytic agent cis-dichlorodiammineplatinum-II.

In vitro drug metabolism from liver and kidney of rats was studied for up to 12 days following a single intraperitoneal injection of the antineoplastic drug cisplatinum. At 3,5, and 8 days posttreatment, hepatic cytochrome P-450 dependent enzyme activity was increased 20-45%, but levels of cytochromes P-450 and b5 were unaltered. Hepatic in vitro stimulated thiobarbituric acid reactive (TBAR) substances were increased at all times, with a maximum of 20 times normal on day 5. Renal aniline hydroxylase activity was elevated 25-95% throughout the first 8 days. Renal in vitro stimulated TBAR substances were not significantly altered. In vitro addition of cisPt to control microsomes resulted in no consistent, dose-related changes in substrate metabolism.