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In 32 women of normal body weight who volunteered to participate in the study, the effect of rapid weight reduction by a low-calorie liquid diet on serum lipids and lecithin:cholesterol acyltransferase (LCAT) enzyme activity was studied. Women were on this 400 kJ/day diet for 7 days and fasting blood samples were drawn before and immediately after the diet. Serum cholesterol decreased from 5.7 +/- 1.0 to 5.2 +/- 1.1 mmol/l and high density lipoprotein cholesterol from 1.77 +/- 0.43 to 1.50 +/- 0.35 mmol/l. The serum LCAT activity decreased significantly during the weight reduction period. When serum LCAT activity was correlated to lipid parameters, a positive correlation was found with total cholesterol and triglyceride concentrations before weight reduction and also between changes in LCAT activity and total cholesterol concentration. The data suggest that serum LCAT activity might have a prominent role in the regulation of serum lipid levels.

The inducibility of the mucosal drug-metabolizing enzymes of rat small intestine was studied by administering 3-methylcholanthrene either intragastrically or intraperitoneally. The aryl hydrocarbon hydroxylase activity was 4.1 times higher after intragastric than after intraperitoneal administration of methylcholanthrene. The ethoxycoumarin-O-diethylase activity was 11 times and UDP-glucuronosyltransferase (with p-nitrophenol as substrate) activity was 3 times higher after intragastric administration than after intraperitoneal administration. The epoxide hydratase activity was, on the other hand, 38% lower after intragastric administration of 3-methylcholanthrene than after intraperitoneal administration. The results suggest that compounds entering the body intragastrically, e.e. in the diet, might have profound enzyme-specific effects on the intestinal metabolic rates of drugs.