Ontogenesis of K and Na fluxes in embryonic chick heart

Abstract

Cation analyses showed that ventricular and atrial K increased gradually during early embryogenesis, reached a plateau by 13 days, and then decreased at hatching. Myocardial Na was extremely high at 2 days, fell markedly by 7 days, and then more gradually through hatching. K influx and efflux in isolated ventricles were relatively high at 7 days, fell at 13 days, and then increased shortly after hatching. Intracellular K exchangeability was relatively constant throughout development at 70%. Na exchange was more complex than K. Intracellular Na exchangeability was only 7% at 7 days, but rose gradually during development to 73% shortly after hatching. The presence of an active transport mechanism in the embryo heart by at least 2 days of incubation was suggested. Enzymatic and electrophysiological correlates were discussed.