Sarcolemmal Na+-Ca2+ exchange and sarcoplasmic reticulum Ca2+ uptake in several cardiac preparations.

Calcium transport mediated by the sarcolemma (SL) Na+-Ca2+ exchanger and by the sarcoplasmic reticulum (SR) Ca2+ pump were studied in crude membranes from ventricular tissue of newborn and young rat, adult frog, guinea pig, chick, hamster, Rhesus monkey, rabbit, and pig. Transport activities were evaluated per mass of membrane protein and heart tissue. Relative to unit of ventricular mass Na+-Ca2+ exchange activity (at [Ca2+] = 75 microM) is highest in newborn rat, frog, guinea pig, and chick amounting to about 17.

Developmental changes of Ca++ transport systems in chick heart.

Sarcolemma (SL) Na+/Ca++ exchange, binding of the Ca++ channel antagonist [3H]nitrendipine and sarcoplasmic reticulum (SR) Ca++ uptake were studied in crude membranes from developing chick heart. Energy-linked Ca++ uptake of mitochondria (MT) was measured in tissue homogenates. When reckoned per unit of heart mass Na+/Ca++ exchange increases linearly (20-fold) from embryonic day 4 to postnatal day 10.

Comparative analysis of phospholamban phosphorylation in crude membranes of vertebrate hearts.

Phospholamban, a sarcoplasmic reticulum phosphoprotein, is present in the hearts of mammalian, avian, amphibian, and fish species. Phylogenetic changes are indicated by marked differences among species in cardiac phospholamban content and by the absence of Ca2+/calmodulin-dependent phospholamban phosphorylation at an early developmental stage.

Early presence of phospholamban in developing a chick heart.

Phosphorylation of phospholamban and development of reticular Ca2+ transport were studied in crude membrane preparations of embryonic, newborn and adult chick heart. Maximal phosphorylation of phospholamban by added catalytic subunit of cyclic AMP-dependent protein kinase increases from embryonic day 4-15. It decreases with further development.