Inducibility of hepatic drug metabolizing enzymes during fat deficiency

The influence of dietary energy levels with and without PCB induction on the growth of tilapia, Oreochromis niloticos x O. aureus

The effects of three dietary energy levels, 323, 365 and 408 Kcal/100g diet, on the growth performance of hybrid tilapia, Oreochromis niloticus x O. aureus, were studied. The experiment was carried out for 3 months in a recirculating rearing system. Growth and feed conversion ratios were significantly reduced (p<0.05) in fish exposed to 100 ppm polychlorinated biphenyl (PCB), fed high energy diets (365 and 408 Kcal/100g diet). The hepatic cytochrome P-450 and NADPH-cytochrome c reductase activities were also significantly (p<0.05) lower in PCB-treated fish fed high energy diets (365 and 408 Kcal/100g diet) than fish fed lower energy diet (323 Kcal/100g diet). The malic enzyme activity and the body lipid content in fish generally increased as the dietary energy level increased.

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.

The effects of dietary corn oil on the metabolism and mutagenic activation on N-nitrosodimethylamine (DMN) by hepatic microsomes from male and female rats

Microsomes from male and female rats fed a diet containing 10% corn oil metabolized N-nitrosodimethylamine (DMN) more rapidly than microsomes from rats fed a similar diet devoid of corn oil. The daily administration of phenobarbital for 4 days prior to harvesting the microsomes resulted in significant induction of the Vmax for N-demethylation of DMN in rats fed the fat-free diet but resulted in no induction (females) or suppression (males) of this enzyme in rats fed the diet containing corn oil. Using concentrations of DMN ranging from 12 to 100 mM, microsomes from rats fed the high fat diet activated DMN to produce mutagenesis in S. typhimurium (TA100) more rapidly than those from rats fed the fat-free diet. Phenobarbital administration induced this activation more effectively in rats fed the corn oil diet than in rats fed the fat-free diet. Phenobarbital induces DMN N-demethylation in rats fed both fat-free and 10% corn oil diets when the DMN concentration is above 10 mM and explains, at least in part, this enhanced mutagenic activation.