Biochemical studies on ovine pregnancy toxaemia. I. Enzymic activities of liver and brain

Abstract

Enzymic activities in vitro of liver and brain tissue of sheep with pregnancy toxaemia were measured. Anaerobic glycolysis and oxidations of tricarboxylic acid cycle intermediates and related substrates were normal for both brain and liver enzyme preparations. Fatty acid oxidation by liver mitochondria was abnormal. Liver mitochondria from cases of pregnancy toxaemia were invariably incapable of oxidizing octanoate and palmitate, and frequently unable to oxidize propionate. The rate of propionate oxidation was low even when this substrate was oxidized. Butyrate oxidation was not much reduced by pregnancy toxaemia. Starvation of ewes in late pregnancy did not inactivate the fatty acid oxidation chains of liver mitochondria. Possible reasons for the failure of lipid metabolism are discussed. The dependence of sheep liver metabolism upon fatty acid oxidation is discussed. Insignificant amounts of glucose are absorbed from the alimentary canal in sheep and, even if absorbed, are not catabolized to supply acetyl coenzyme A for oxidation in the tricarboxylic acid cycle. Consequently sheep liver is prone to failure from interference with fatty acid oxidation. Pregnancy toxaemia is discussed in relevance to the disturbance of fatty acid metabolism which is thought to be of considerable significance in the disease.