Delineation of high and low affinity calcium 45 incorporation and of calcium 45 efflux in canine aortic smooth muscle microsomes

Kutsky, P.; Weiss, G.B.; Karaki, H.

General Pharmacology 11(6): 475-482


ISSN/ISBN: 0306-3623
Accession: 005101889

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Scatchard plots of Ca2+ incorporation in canine aortic media-intima microsomes indicate 2 types of binding sites. Low affinity binding sites equilibrate more rapidly. Ca2+ incorporation is higher in a NaCl medium than in a KCl medium at a Ca2+ concentration in which high affinity binding predominates. The high affinity 45Ca binding is largely ATP-dependent. Efflux of non-superficial 45Ca from the microsomes is linear during a 32-min washout into a solution containing no added Ca2+ and is increased by addition of 0.1 mM EGTA [ethylene glycol bis(.beta.-aminoethyl ether) N,N,N',N'-tetraacetic acid], 1 mM Ca2+ or 1 mM Sr2+.