The response of the early chick embryo heart to anoxia

Abstract

Isolated 3-and 5-day chick embryo hearts contain sufficient endogenous substrates to maintain their pulsatile activity for several hours under aerobic conditions, and even after five hours in substrate-free medium the rates are 40 to 50% of the original rates. Carbohydrate appears to be an important component of the endogenous substrates since 1 mM 2-deoxyglucose causes rapid failure of rate, and glycolysis appears to be a major energy pathway since the rate is depressed only about 50% by 2-hour's exposiire t o 10mM fluoroacetate. In nitrogen the hearts rapidly become asystolic in the absence of added substrate. Recovery of the rate occurs if oxygen is reintroduced within one hour, but longer periods of anoxia result in progressively less recovery, especially with the 3-day hearts which appear to be particularly susceptible to irreversible damage. With 5.55 mM glucose as substrate there is little decrease in the original aerobic heart rate during five hours, and the hearts can tolerate total anoxia for five hours with rates only slightly less than the aerobic rates. The hypothesis of a preferential pentose phosphate pathway of glucose catabolism in the very young chick embryo heart is discussed, but no direct evidence in support of its existence is revealed in this study.

Cellular Energy Metabolism During Fetal Development

“…This suggests that glucose may be preferentially oxidized by the developing heart . It has been well established that anaerobic glycolysis and the hexose monophosphate shunt are active metabolic pathways during early development (17)(18)(19)(20)(21) . The presence of abundant glycogen in the fetal heart is another indication of the importance of carbohydrate as a substrate (22) .…”