Abstract
The objective of this investigation was to study the responses of hepatic soluble fatty acid synthetase (FAS) and microsomal glycerophosphate acyltransferase (GPAT) to qualitative and quantitative differences in dietary fats and the effects on those enzymes of fasting and refeeding following a fast. Also investigated were the interrelationship between dietary fat, tissue fatty acids and enzymic activity in the soluble and microsomal fractions. FAS activities of livers of rats consuming the fat-free (FF), or the 2.5% or 5% cocoa butter (CB) diets for one week were equal. However, 2.5% and 5% safflower oil (SO) diets reduced FAS activity by 25% and 40% respectively. FAS activities of livers of rats consuming stock diet or fasting for three days were 20% and 5% respectively of those on the FF diet. However, fasting for three days followed by feeding FF, 5% SO or 5% CB resulted in hyper-stimulation of the FAS to peak activities in two days. Thus fat in the diet, saturated or unsaturated, did not inhibit adaptive increase in FAS activity during the first few days of feeding after a fast. However, at the seventh day of refeeding there was a highly significant reduction in FAS of rats fed 5% SO compared to those fed either FF or 5% CB diets. Standard GPAT assay conditions were developed using microsomes from rats maintained on a stock diet. Neither fasting for three days nor ingestion of diets containing 2.5%, 5%, 10%, or 15% CB or SO for one week altered GPAT as compared to stock or FF diets. The average specific activity of GPAT for these dietary treatments was 5.1 nano-moles phosphatidate synthesized per minute per mg microsomal protein..
Wiegand, Rex Dale (1973). Dietary regulation of fatty acid synthetase and microsomal glycerophosphate acyltransferase activities in rat liver. Doctoral dissertation, Texas A&M University. Texas A&M University. Libraries. Available electronically from
https : / /hdl .handle .net /1969 .1 /DISSERTATIONS -158466.