Inhibition of Na+-Ca2+ exchange in rat brain by amiloride.
Amiloride (N-amidino-3,5-diamino-6-chloropyrazine carboxamide) reversibly inhibits Na+-dependent 45Ca2+ uptake (Na+-Ca2+ exchange) by plasmalemma-enriched vesicles prepared from microsomes of rat cerebral cortex and by vesicles from osmotically shocked synaptosomes. The drug inhibits Na+-dependent Ca2+ uptake in a competitive manner with a KI of 0.25-0.34 mM. Na+-dependent 45Ca2+ efflux from vesicles is also inhibited by extravesicular amiloride. The drug does not appear to affect nonmitochondrial ATP-dependent Ca2+ transport in these vesicle preparations. Membranes containing Na+-Ca2+ carrier can be solubilized in Na+-cholate and reconstituted into phospholipid vesicles. Na+-dependent Ca2+ uptake by the vesicles is inhibited by amiloride.
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000584:Amiloride / Q000494:pharmacology*; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D066298:In Vitro Techniques; D008297:Male; D008861:Microsomes / Q000378:metabolism; D011719:Pyrazines / Q000494:pharmacology*; D051381:Rats; D012964:Sodium / Q000378:metabolism*
D011719:Pyrazines; D000584:Amiloride; D000255:Adenosine Triphosphate; D012964:Sodium; D002118:Calcium