Arterial enzymes and their relation to atherosclerosis in pigeons

Abstract

Comparison of metabolic processes between the atherosclerosis-resistant Show Racer (SR) and susceptible White Carneau (WC) pigeon strains offers an opportunity to study factors which may predispose to atherosclerosis. The activity of several glycolytic enzymes, Krebs cycle enzymes, enzymes of the ATP cycle and of the glycerol phosphate shuttle was studied in SR and WC arteries.In 4–6 yr old pigeons the activity of lipoamide dehydrogenase and malate dehydrogenase is significantly lower in WC than SR arteries. The differences are not the result of aging or atherosclerosis, because they were also detected in arteries of very young 5–8 wk old pigeons. Furthermore, the arteries of the young pigeons revealed a significantly higher activity of two glycolytic enzymes, namely phosphofructokinase and aldolase, in the WC arteries as compared with SR arteries.The results in the young birds indicate that the differences between the two pigeon strains are of an inherited (genetic?) nature. It is suggested that low activity of lipoamide and malate dehydrogenases slows down the Krebs cycle and leads to low citrate and ATP production. The latter factor is an essential part of the feedback control adjustments that regulate the efficiency of glycolysis via phosphofructokinase. Increased dependence of the WC arteries on glycolysis appears to facilitate the development of atherosclerosis in these birds, and the mechanism may be similar to the mechanism by which tissue hypoxia induces lipid accumulation and connective tissue alterations in the arterial wall.An additional finding in these studies is the higher activity in female than male arteries of phosphofructokinase, aldolase, isocitrate dehydrogenase, glycerokinase, ATPase and creatine phosphokinase.