Regulation of hepatic drug metabolism by elaidic and linoleic acids in rats

B-naphthoflavone induction and its effect on hepatic phospholipid metabolism in rainbow trout (Salmo gairdneri)

1. B-naphthoflavone (BNF) induction of microsomal cytochrome P-488 and its effect on liver phospholipid metabolism were examined in rainbow trout (Salmo gairdneri) 24 and 96 hr after intraperitoneal injection. 2. Cytochrome P-448 content increased at 96 hr to approximately double the cytochrome content of control fish. 3. Computer-analyzed laser densitometry scans of LDS-polyacrylamide gels of 96 hr BNF-treated liver microsomes showed a 90% increase in cytochrome P-448 levels. 4. A 34% increase in microsomal phospholipid (mumol/mg protein) was observed 24 hr after BNF injection, with a marked increase in choline, ethanolamine and inositol phospholipids. 5. Following 96 hr of exposure to BNF some differences in enzyme activity were noted; choline kinase and cytidylyltransferase activities were reduced, while a marked increase was observed in choline phosphotransferase activity. In light of current information on induction of liver microsomal phospholipid metabolism in mammals, the results of the this study suggest that trout do not respond like mammals to inducers of monooxygenase activity.

Activities of liver mixed function oxidase system in rats fed trans fat

Rats were fed diets containing either camellia oil or partially hydrogenated corn oil as a source of cis or trans octadecenoate, respectively, in the presence of adequate linoleic acid. After 35 days of feeding the diets, activities of several hepatic drug metabolizing enzymes as well as the content of hepatic microsomal cytochrome P-450 were determined. Geometrical difference in the dietary fat did not affect the amount of microsomal protein nor the content of cytochrome P-450. Also, activities of NADPH cytochrome C reductase, aminopyrine N-demethylase and biphenyl hydroxylase were approximately the same between two groups of rats. Aniline hydroxylase was slightly elevated in the rats fed trans fat. It was concluded that the difference in the geometry of dietary fatty acids had little effect in modulating the hepatic mixed function oxidase system.

Liver microsome phospholipids and cytochrome P.450 concentration in phenobarbital treated rats fed on different diets

Liver microsomal concentration of cytochrome P.450 is increased in animals which are fed diets rich in polyunsaturated fatty acids. On the other hand, the effects of phenobarbital are more important when the dietary fat is more unsaturated. The unsaturation index in liver microsomal phosphatidylcholines depends on the unsaturation of the dietary fats. The treatment with phenobarbital constantly results in a decrease of the unsaturation index of fatty acids both in lecithins and cephalins. The importance of the liver microsomal cytochrome P.450 increase and the importance of the unsaturation index decrease in liver microsomal lecithins, both promoted by phenobarbital, are in good agreement.

Variations in the glucuronidation rate and in the composition of the endoplasmic reticulum of the wild and semi-domestic reindeer (Rangifer tarandus)

1. The activity of UDPglucuronosyltransferase was analyzed in the hepatic and renal microsomes and in the postmitochondrial supernatant fraction of the duodenal mucosa of wild and semi-domestic reindeer. 2. The total activity was about the same in the hepatic microsomes of both animal groups. When the specific activity was analyzed, the semi-domestic reindeer showed twice as high activities as the wild ones. 3. The results in the kidney and duodenum showed similar changes. 4. The protein, cholesterol and phospholipid concentrations of microsomal and postmitochondrial supernatant preparations were higher in the wild reindeer. 5. It is concluded on the basis of present results that the in vitro glucuronidation in the wild reindeer is on a lower level than in the semi-domestic ones. 6. This might be a consequence of changed membrane structure where UDPglucuronosyltransferase is located.

Hepatic drug metabolism during ethanol ingestion in riboflavin deficient rats

Riboflavin deficiency was induced by feeding rats a riboflavin-deficient diet for 1 month. In order to find out if there are any combined effects of ethanol and riboflavin deficiency on drug metabolism, a group of riboflavin-deficient rats were also given ethanol in their drinking water. At the end of the feeding period, hepatic drug-metabolizing enzyme activities were determined. The hepatic phospholipid and protein contents were the same in rats receiving a standard diet and in those on a riboflavin-deficient diet. However, ethanol ingestion in both groups enhanced significantly the phospholipid content. Ethanol ingestion also markedly enhanced the hepatic cytochrome P-450 concentration in rats fed either a standard or riboflavin-deficient diet. Ethoxycoumarin O-deethylase activity was significantly lower in riboflavin-deficient rat livers than in those of the controls. In both groups ethanol ingestion nearly doubled the activities. Aryl hydrocarbon hydroxylase activity was also significantly decreased during riboflavin deficiency. However, ethanol administration did not change the activities of this enzyme. UDP glucuronosyltransferase activity was slightly lower in riboflavin-deficient rat livers than in those fed a standard diet. No significant decrease was found in the epoxide hydrase activity in the riboflavin-deficient rats. However, the riboflavin-deficient rats had enhanced activity after the ethanol ingestion.

The copper induced modification of duodenal biotransformation reactions in rats during fat deficiency

The effect of ingested copper on the composition of duodenal postmitochondrial supernatnat fraction (PMS), the aryl hydrocarbon hydroxylase (AHH) and UDPglucuronosyltransferase (GT) activities was analyzed in rats given normal or fat free diets. There were only minor changes in the composition of PMS or in the activities of the measured enzymes when rats received a normal diet. During fat deficiency the phospholipid-protein ratio and the GT activity were markedly increased following 10 mM copper concentration in the drinking water. It is concluded that during fat deficiency copper modifies the structure of the microsomes, as analyzed in the PMS, and that this is reflected in the membrane bound GT activity.