Différences de nature dans les systèmes de transport extra-mitochondrial des précurseurs de la synthèse des acides gras chez le rat et la souris

Abstract

Summary A comparative study of the extramitochondrial carriers of precursors for fatty acid synthesis in rats and mice has been made. Animals treated with amino-oxyacetate (AOA) received intravenous injections of either [2-3H] acetate or [2-14C] pyruvate and killed 5 min thereafter. In rats, the radioactivity found in liver fatty acids increases when the precursor is [2-3H] acetate but not when it is [2-14C] pyruvate. On the contrary, an inhibition of fatty acid synthesis is observed in mice mainly after administration of [2-14C] pyruvate. Administration of AOA results in inhibition of gluconeogenesis from [2-14C] pyruvate in rats but a stimulation is observed in mice. AOA does not modify the intracellular distribution of neo-synthesized fatty acids in rat liver. The activity of hepatic citrate cleavage enzyme of rats is twice that of mice. The incorporation of tritium of 3H2O (which is not submitted to dilution phenomena) in the fatty acids of rats and mice has also been studied as a function of time. AOA inhibits fatty acid synthesis in mouse adipose tissue and liver at all time intervals studied. However, only a slight inhibition was observed in rat liver. Varying concentrations of pyruvate do not influence the stimulatory effect of AOA on the incorporation of [2-3H] acetate but the administration of citrate suppresses it. The results are discussed and it is concluded that in the liver, citrate is a more efficient carrier of acetyl CoA in rats than in mice and that extramitochondrial carriers of precursors for fatty acid synthesis are different in rats and mice.