Depletion of ▵9 desaturase (EC 1.14.99.5) activity in lactating rat during protein restriction

Abstract

The effects of protein restriction on the activity of ▵9 desaturase (EC 1.14.99.5) were investigated in lactating rats. A control group was fed a balanced diet (20% casein) for 14 days, whereas the experimental groups were fed a low-protein diet (8% casein), supplemented with or without L-methionine (0.4%), for 14 days. The enzyme activity was measured by incubations of hepatic microsomal pellets with (1-14C) stearic acid. Results showed a decreased ▵9 desaturase activity, after 2,7 and 14 days of depleted diet, of –50, –40 and –33% respectively, compared with control. The supplementation of the low-protein diet with 0.4% methionine, which favours food consumption as well as growth, did not improve the altered ▵9 desaturase activity. Our data evidenced that ▵9 desaturase activity is depleted by protein restriction during lactation, when the protein needs are high for the biosynthesis of animal tissues. This change has to be considered as a sign of depressed ▵9 desaturase biosynthesis or modifications of enzymatic properties, or both.