Étude chronologique des effets d'un régime hypoprotéique suivi d'un régime équilibré sur les DL6-et DL5-désaturations de l'acide linoléique des microsomes hépatiques de rat

Abstract A low protein diet affects amounts of linoleic and arachidonic acids in hepatic microsomal phospholipids of growing rats. Are the changes related to modifications in microsomal DL6-and DL5-linoleic acid desaturase activities? Two groups of Wistar rats weighing 80 5 g at the beginning of the experiment were used: Control group (T) was fed on a 16% gluten + 4% casein diet for 53 days; Experimental group (E) was fed on a 4% gluten + 1% casein diet for 26 days (MP) then Control diet for 27 days (RE). After 2, 14 and 26 days of MP and 2, 15 and 27 days of RE, rats of each group were sacrificed. Protein and water contents of liver, quantitative fatty acid, composition of total lipids in liver and hepatic microsomes were determined. DL6-and DL 5-linoleic acid desaturase activities were estimated from incubation of liver microsomes with [1-14C] C 18: 2 n-6 or [214C] C 20: 3 n-6 respectively. The low protein diet stops practically ponderal growth. The fatty-acid compositions of microsomal total lipids of E rats were affected in comparison with values of T rats. These modifications persist after 27 days of RE. The C 20: 4 n-6/C 18: 2 n-6 ratio in microsomal total lipids was slightly different between T and E rats but increased strongly during refeeding. Same modifications take place in the fatty-acid composition of hepatic total lipids. After two days of MP, DL6-and DL5-desaturase activities were depressed, phenomenon that not persist in the course of MP. These enzyme activities increase to higher values than those of the T after two days of RE.