Na-Ca exchange in vascular smooth muscle sarcolemmal vesicles is voltage sensitive and inhibitable by quinidine and diltiazem

Conference · Wed Mar 05 04:00:00 EST 1986 · Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States)

OSTI ID:6992037

Kahn, A M; Allen, J C

These studies were performed to characterize Na-Ca exchange in a sarcolemmal enriched vesicle fraction, obtained by Mg aggregation and differential centrifugation of homogenized bovine superior mesenteric artery (SMA). To avoid the effects of Ca or Na diffusion potentials on the translocation of the counter ion, the transport of /sup 45/Ca or /sup 22/Na was measured in vesicles which were short-circuited by presetting K/sub in/ = k/sub out/ in the presence of the K ionophore, valinomycin. The uptake of 0.1 mM Ca/sub out/ was stimulated 30% by 150 mM Na/sub in/ versus N-methylglucamine/sub in/, in a control cation. The uptake of ImM Na/sub out/ was stimulated 61% by 10 mM Ca/sub in/ versus Mn/sub in/. The efflux of ImM Na/sub in/ was stimulated 57% by 10 mM Ca/sub out/ versus Mn/sub out/. Thus, these vesicles mediate Na/Ca exchange. The one sec Na gradient-dependent uptake of 0.1 mM Ca/sub out/ was .08 nmol/mg under short-circuited conditions. When the membrane potential was rendered inside positive by an inwardly directed K gradient plus valinomycin, Na gradient-dependent Ca uptake increased to 0.17 nmol/mg. The Na gradient-dependent uptake of 0.1 mM Ca/sub out/ was inhibited 12, 6, 82, and 70% by (in mM) 5 choline, 3 amiloride, 5 quinidine, and 5 diltiazem, respectively. It is concluded that Na-Ca exchange in the sarcolemmal of bovine SMA is voltage sensitive, and inhibitable by quinidine and diltiazem. Depolarization stimulated Ca influx in vascular smooth muscle cells may occur, in part, via Na-Ca exchange.

• Research Organization: Univ. of Texas Medical School, Houston
• OSTI ID: 6992037
• Report Number(s): CONF-8604222-
• Conference Information: Journal Name: Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States) Journal Volume: 45:4
• Country of Publication: United States
• Language: English

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59 BASIC BIOLOGICAL SCIENCES
ALKALI METALS
ALKALINE EARTH ISOTOPES
ALKALINE EARTH METALS
ARTERIES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BLOOD VESSELS
BODY
CALCIUM
CALCIUM 45
CALCIUM ISOTOPES
CARDIOVASCULAR SYSTEM
DAYS LIVING RADIOISOTOPES
ELEMENTS
EVEN-ODD NUCLEI
INTERMEDIATE MASS NUCLEI
ISOTOPE APPLICATIONS
ISOTOPES
MEMBRANE TRANSPORT
METALS
MUSCLES
NUCLEI
ORGANS
PHYSIOLOGY
RADIOISOTOPES
SODIUM
TRACER TECHNIQUES