Characterization of Na/Ca exchange in plasmalemmal vesicles from zona fasciculata cells of the bovine adrenal gland.
The presence of an Na/Ca exchange system in fasciculata cells of the bovine adrenal gland was tested using isolated plasmalemmal vesicles. In the presence of an outwardly Na(+) gradient, Ca(2+) uptake was about 2-fold higher than in K(+) condition. Li(+) did not substitute for Na(+) and 5 mM Ni(2+) inhibited Ca(2+) uptake. Ca(2+) efflux from Ca(2+)-loaded vesicles was Na(+)-stimulated and Ni(2+)-inhibited. The saturable part of Na(+)-dependent Ca(2+) uptake displayed Michaelis-Menten kinetics. The relationship of Na(+)-dependent Ca(2+) uptake versus intravesicular Na(+) concentration was sigmoid (apparent K(0.5) approximately 24 mM; Hill number approximately 3) and Na(+) acted on V(max) without significant effect on K(m). Na(+)-stimulated Ca(2+) uptake was temperature-dependent (apparent Q(10) approximately 2.2). The inhibition properties of several divalent cations (Cd(2+), Sr(2+), Ni(2+), Ba(2+), Mn(2+), Mg(2+)) were tested and were similar to those observed in kidney basolateral membrane. The above results indicate the presence of an Na/Ca exchanger located on plasma membrane of zona fasciculata cells of bovine adrenal gland. This exchanger displays similarities with that of renal basolateral cell membrane.
Brunold
C
C
Université Claude Bernard, UMR CNRS 5578, Laboratoire de Physiologie des Eléments Excitables, Villeurbanne, France.
Guyot
A
A
Noble
D
D
Rougier
O
O
Bilbaut
A
A
Ojeda
C
C
D000311:Adrenal Glands / Q000166:cytology / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002417:Cattle; D002462:Cell Membrane / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*; D019831:Sodium-Calcium Exchanger / Q000037:antagonists & inhibitors / Q000378:metabolism; D015383:Zona Fasciculata / Q000166:cytology / Q000378:metabolism*
D019831:Sodium-Calcium Exchanger; D012964:Sodium; D002118:Calcium