Induction of hepatic drug metabolizing enzymes by DL-methionine in rats

A protein inhibitor of hepatic drug metabolizing enzymes from Ehrlich ascites cells

Hepatic drug metabolizing enzymes were significantly decreased in Ehrlich ascites tumour-bearing mice. A protein inhibitor of hepatic drug metabolizing enzymes was isolated from Ehrlich ascites cells and purified. This involved ammonium sulphate fractionation (60-80%), DEAE, phosphocellulose, Sephadex G-100 and hydroxyapatite column chromatography. Purification attained was 800-fold. The inhibitory protein was effective in decreasing all the components of hepatic mixed-function-oxidase system and drug metabolizing enzymes both in vivo and in vitro. This novel inhibitor may have potential applications in chemical carcinogenesis.

Nicotinamide-induced modification of hepatic MFO systems in tumour-bearing rats, treated with anti-cancer drugs

Chemotherapeutic drugs like cyclophospamide (100 mg/kg b.wt.) and 5-fluorouracil (120 mg/kg b.wt.) caused significant inhibition in cytochrome P450 (cytP450)-dependent hepatic microsomal drug metabolising enzymes in rats. A similar decrease in these enzyme activities was also seen in the host liver of tumour-bearing animals. However, a non-toxic, endogenous (vitamin B3) metabolite, nicotinamide (100 mg/kg b.wt.) could effectively restore the hepatic drug metabolising enzyme levels back to control values in tumour-bearing animals treated with cyclophospamide and 5-fluorouracil.

Nutritional requirements for detoxication of environmental chemicals

The biological defence systems against oxygen radical toxicity and chemical toxicity, and their component enzymes, are described, and the nutritional requirements for biological defence against chemical and oxygen toxicity, including calories, protein, lipids and lipotropes, vitamins and minerals, are reviewed in the context of their contribution to the mechanisms of detoxication. Modulation of the cytochromes P-450, and hence toxicity, by dietary components are considered; the P450I family, induced by food pyrolysis mutagens, and the P450IIE family, induced by alcohol and fasting, contribute substantially to chemical toxicity and carcinogenicity. It is concluded that: (i) the detoxication system of terrestrial fauna has evolved over greater than 300 million years to protect animals from dietary plant toxins; (ii) protection against chemical and oxygen toxicity requires all categories of nutrients; and (iii) the rôle of food and nutrition in detoxication is essential to survival.