NO contribution to lipopolysaccharide-induced hepatic damage in galactosamine-sensitized mice.
To investigate the role of nitric oxide (NO) in hepatitis-induced endotoxemia, we injected mice intraperitoneally with 250 mg/kg galactosamine (GalN) and 1 mg/kg lipopolysaccharide (LPS) separately and in combination. NO synthesis increased in a dose-dependent manner with LPS. NO generation at 5 hr after administration of LPS was greater than that at 24 hr. Enhancement of NO generation was demonstrated in mice administered GalN and LPS in combination. A nitrosyl-heme signal in 10,000 g supernatant of liver homogenate, due to cytochrome P450 (P450) combining with NO, NO-P450, was detected at more than ten hr and even more after administration of LPS by electron spin resonance (ESR) measurements at 77 degrees K. The strongest NO-P450 signal and most extreme elevation of aspartate oxoglutarate aminotransferase (AST), alanine oxoglutarate aminotransferase (ALT), and lactate dehydrogenase (LDH) in serum and of lysosomal enzyme activity in plasma were observed in the GalN + LPS group. Their potency was greater than in the 10 mg/kg LPS group, which was even greater than in the LPS 1 mg/kg group. The aniline hydroxylase activity was inversely proportional to NO-P450 signal intensity. It appears that NO might contribute to LPS-induced hepatic damage in GalN-sensitized mice through degeneration and inactivation of liver microsomal enzymes by binding P450 active sites. (+info)
Studies on the cytochrome P450 (CYP)-mediated metabolic properties of miocamycin: evaluation of the possibility of a metabolic intermediate complex formation with CYP, and identification of the human CYP isoforms.
Some macrolide antibiotics cause clinical drug interactions, resulting in altered metabolism of concomitantly administered drugs, via the formation of a metabolic intermediate (MI) complex with cytochrome P450 (CYP), or competitive inhibition of CYP. In this study, the possibility of MI complex formation by miocamycin (MOM) was assessed first. CYP contents and activities in rat liver microsomes were not affected and there were no detectable MI complexes after administration of MOM for either 3 or 10 days to rats. Furthermore, MOM did not form MI complexes in vitro even with microsomes from humans or dexamethasone-pretreated rats. Second, in vitro studies were conducted to identify the human CYP isoforms involved in four 14-hydroxylation reactions in the MOM metabolic pathway. The results showed that it was most likely CYP3A4 involved in the hydroxylations: 1) each hydroxylation in human liver microsomes from 10 different donors strongly correlated with testosterone 6 beta-hydroxylation; 2) each hydroxylation was essentially inhibited by ketoconazole and troleandomycin; 3) only cDNA-expressed CYP3A4 and CYP3A5 catalyzed the hydroxylations, and the activities of CYP3A5 were below 5% of those of CYP3A4; and 4) the apparent K(M) values obtained with native human liver microsomes were comparable with those obtained with cDNA-expressed CYP3A4. In conclusion, MOM is not an inhibitor of CYP via the formation of an MI complex. Moreover, CYP3A4 is mainly responsible for catalyzing the hydroxylation of MOM metabolites. Because CYP3A4 is the most abundant form of CYP in the liver and intestine, this isoform probably accounts for the majority of drug-MOM interactions observed in clinical practice. (+info)
Studies on the evaluation of the toxicity of various salts of lead, manganese, platinum, and palladium.
Preliminary studies have been conducted on various parameters in order to assess the possible and relative toxicities of a number of metallic salts. Upon oral administration in lethal-dose experiments, two soluble Pt4+ salts were more toxic than the other salts tested. Following intraperiotneal injection in lethal-dose experiments, PbCl2 was less toxic than several of the soluble or partially soluble salts of Pt4+, Pd2+, and Mn2+. An intake of a total of approximately 250 mg of Pt4+ per rat in the drinking fluid over a 30-day interval did not affect the activities of aniline hydroxylase and aminopyrine demethylase in rat liver microsomes. In rats receiving soluble Pt4+ salts in the drinking fluid, the highest concentration of Pt was found in the kidney and an appreciiable concentration was found in the liver. (+info)
Dietary saturated fatty acids reverse inflammatory and fibrotic changes in rat liver despite continued ethanol administration.
We investigated the potential of dietary saturated fatty acids to reverse alcoholic liver injury despite continued administration of alcohol. Five groups (six rats/group) of male Wistar rats were studied. Rats in groups 1 and 2 were fed a fish oil-ethanol diet for 8 and 6 weeks, respectively. Rats in groups 3 and 4 were fed fish oil and ethanol for 6 weeks before being switched to isocaloric diets containing ethanol with palm oil (group 3) or medium-chain triglycerides (MCTs, group 4) for 2 weeks. Rats in group 5 were fed fish oil and dextrose for 8 weeks. Liver samples were analyzed for histopathology, lipid peroxidation, nuclear factor-kappaB (NF-kappaB) activation, and mRNAs for cyclooxygenase-2 (Cox-2) and tumor necrosis factor-alpha (TNF-alpha). Endotoxin in plasma was determined. The most severe inflammation and fibrosis were detected in groups 1 and 2, as were the highest levels of endotoxin, lipid peroxidation, activation of NF-kappaB, and mRNAs for Cox-2 and TNF-alpha. After the rats were switched to palm oil or MCT, there was marked histological improvement with decreased levels of endotoxin and lipid peroxidation, absence of NF-kappaB activation, and reduced expression of TNF-alpha and Cox-2. A diet enriched in saturated fatty acids effectively reverses alcohol-induced necrosis, inflammation, and fibrosis despite continued alcohol consumption. The therapeutic effects of saturated fatty acids may be explained, at least in part, by reduced endotoxemia and lipid peroxidation, which in turn result in decreased activation of NF-kappaB and reduced levels of TNF-alpha and Cox-2. (+info)
Leaves from a standard, insect-susceptible cauliflower variety and an insect-resistant strain were formulated at either 10 or 25% into semipurified diets for male and female weanling rats. After 3 weeks, relative liver weights, microsomal protein, cytochrome P-450, and activities of hepatic microsomal aminopyrine N-demethylase, aniline hydroxylase, p-nitroanisole O-demethylase, and N-methylaniline N-demethylase were determined. Growth, feed intake, and feed efficiency of male rats were not affected by the inclusion of the dried cauliflower leaf in the diet. However, female rats exhibited a depressed feed intake and increased feed efficiency with cauliflower leaf supplemental diets. Relative liver weights increased with increasing percentage of cauliflower leaves in the diet. Hepatic microsomal enzyme response to cauliflower leaf supplementation of the diet was greater in males than in females. Only aniline hydroxylase activity remained unchanged by the test diets. Male rats showed significant increases in N- and O-demethylation with both the 10 and 25% cauliflower diets, and increased values for microsomal protein and cytochrome P-450 at the 25% supplemental level. Female rats did not show significant hepatic microsomal induction from cauliflower leaf consumption at the 10% level. However, cytochrome P-450 and the metabolism of aminopyrine and p-nitroanisole were enhanced by consumption of cauliflower leaves at 25% of their diet. None of the parameters tested in this study evidenced a difference between the two cauliflower cultivars fed to either sex. (+info)
Differential mutagenicities of triamino benzenes against Salmonella typhimurium TA98 in the presence of S9 fractions from polychlorinated biphenyls-, phenobarbital- or 3-methylcholanthrene-pretreated rats, hamsters and mice.
Mutagenicity of 6 aminobenzene derivatives against Salmonella typhimurium TA98 was studied in the presence of various S9 fractions. S9, which has been prepared form the livers of rats, hamsters and mice after pretreatment with different types of inducers; polychlorinated biphenyls, phenobarbital and 3-methylcholanthrene, was used as the methabolic activating enzyme in this mutation assay. The S9 fractions from 3-methylcholanthrene-treated rats and mice are most useful for mutation induction by the all aminobenzenes used. The mutagenic activity of the compounds was clearly correlated to 3-methylcholanthrene-induced cytochrome P-450. However, any significant correlation between aniline hydroxylase activity and the mutagenesis was not observed. (+info)
The differential effects of chemical carcinogens on vitamin A status and on microsomal drug metabolism in normal and vitamin A-deficient rats.
Male Sprague-Dawley rats were maintained on a vitamin A-deficient diet for 5 weeks. Although serum and hepatic levels of vitamin A were significantly lower at this time, no outward signs of vitamin A deficiency were present. Hepatic microsomal levels of cytochrome P-450 in the vitamin A-deficient animals were 70% that of the control animals. Of the three microsomal enzymes studied, ethylmorphine N-demethylase, aniline hydroxylase, and aminopyrine N-demethylase, only the last one was adversely affected by vitamin A deficiency. 3-Methylcholanthrene, phenobarbital, and 2-acetylaminofluorene had a greater inductive effect and cytochrome P-450 in vitamin A-deficient rats. 4-Dimethylaminoazobenzene treatment decreased in the level of cytochrome P-450 in control rats more than in deficieny rats. The hepatic concentration of vitamin A was significantly reduced in control rats that were given injections of 3-methylcholanthrene, 2-acetylaminofluorene, or phenobarbital. Benzo(a)pyrene and 4-dimethylaminoazobenzene had less effect. (+info)
Difference between effects of chlorpromazine and perphenazine on microsomal phospholipids and enzyme activities in rat liver.
The effects of acute administration of chlorpromazine (CPZ) and perphenazine (PPZ) on hepatic microsomal phospholipids (PLs) and enzyme activities in the male rat were examined in order to elucidate the relationship between individual PLs and drug-metabolizing activity. Cytochrome P-450 and aniline (AN) hydroxylation activity were initially decreased in CPZ-treated rats, but cytochrome P-450 subsequently recovered to a level not significantly different from the control and AN hydroxylation was markedly increased, while in PPZ-treated rats, they remained depressed. CPZ increased the activities of glycerophosphate acyltransferase (GPA) and choline phosphotransferase (CPT), while PPZ increased the activities of phosphatidate cytidylyltransferase (PCT), phosphatidate phosphohydrolase (PPH) and CPT. Concurrently, CPZ raised microsomal phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylserine-inositol (PSI) and sphingomyelin (SM), while PPZ increased PC and PE, but did not affect the levels of PSI and SM. Acyl components of phospholipids were also modified. CPZ significantly decreased the ratio of saturated to unsaturated fatty acids, particularly in the PC and PE fractions, while the effect of PPZ was only slight. The results imply that an increase of AN hydroxylation activity may involve the incorporation of unsaturated fatty acids into enzyme-associated PC and PE. (+info)