Developmental changes in Ca(2+)-uptake, Na+,Ca(2+)-exchange and Ca(2+)-ATPase in freshly isolated embryonic, newborn and adult chicken heart.
Developmental changes in cellular Ca(2+)-transport mechanisms were studied in chick heart by determining cellular Ca(2+)-uptake and Na+,Ca(2+)-exchange activity in freshly isolated ventricular tissues of embryonic (5-18 days old), newborn (1-2 days old) and young adult (90-100 days old) heart by monitoring 45Ca influx. Ca(2+)-ATPase activity was determined in microsomal fractions at different stages of development. The Ca(2+)-uptake (per g wet tissue weight) increased with the development of embryonic as well as post-hatch chick heart, reaching a maximum in the young adult chicken. The overall increase in Ca(2+)-uptake, from embryonic day 5 to young-adult stage, was more than 3 fold. The Na+,Ca(2+)-exchange activity, determined as Na(+)-gradient-induced Ca(2+)-uptake in presence of either ouabain or zero [Na+]0, showed a 6-fold increase during development of heart from the embryonic day 5 to the young adult stage. Amiloride, an inhibitor of Na+,Ca(2+)-exchange, caused a dose-dependent reduction in a ouabain-induced rise in 45Ca influx at different stages of development. The inhibitory effect of amiloride was, however, greater during later stages of development. A progressive increase in Ca(2+)-ATPase activity was also seen during development. Ca(2+)-ATPase exhibited about a 4-fold increase in activity from embryonic day 7 to the young adult. The concomitant increase in Ca(2+)-uptake, Na+,Ca(2+)-exchange and Ca(2+)-ATPase activities suggests age-dependent changes in Ca(2+)-transport and storage systems of developing heart during embryogenesis and post-embryonic life. During embryogenesis the developmental increase in Na+,Ca(2+)-exchange activity was greater than that during post-hatch development of heart. However, the increase in Ca(2+)-ATPase activity was greater during post-hatch development than during embryogenesis. It is suggested that Na+,Ca(2+)-exchange and Ca(2+)-ATPase play a prominent role in maintaining cellular Ca2+ homeostasis during embryogenesis and after hatching.
Prakash
P
P
Physiology Division, Central Drug Research Institute, Lucknow, India.
Meera
P
P
Tripathi
O
O
D000818:Animals; D000831:Animals, Newborn; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D002642:Chick Embryo; D002645:Chickens; D006321:Heart / Q000196:embryology / Q000254:growth & development; D066298:In Vitro Techniques; D009206:Myocardium / Q000201:enzymology / Q000378:metabolism*; D012964:Sodium; D019831:Sodium-Calcium Exchanger
D002352:Carrier Proteins; D019831:Sodium-Calcium Exchanger; D012964:Sodium; D000252:Calcium-Transporting ATPases; D002118:Calcium