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Effects of the Ca Agonist Bay K8644 on 45Ca Influx and Net Ca Uptake Into Rabbit Aortic Smooth Muscle

Effects of the Ca Agonist Bay K8644 on 45Ca Influx and Net Ca Uptake Into Rabbit Aortic Smooth Muscle

K S Hwang, C Van Breemen

Eur J Pharmacol. 1985 Oct 22;116(3):299-305.

PMID: 2416574

Abstract:

We examined the effects of Bay K8644 and external K+ on isolated rings of rabbit aorta. Previous evidence has suggested that the Ca channel agonist, Bay K8644, preferentially opens the potential-sensitive Ca2+ channels (PSCs) rather than receptor-operated Ca2+ channels (ROCs). Bay K8644 stimulated 45Ca influx, net Ca gain and contractile tension were measured as a function of extracellular K+ concentration. Although Bay K8644 induced little tension at 5 mM K+ (PSS), Ca2+ influx was stimulated from a resting value of 12 mumol X kg-1 X min-1 (0.02 pmol X cm-2 X s-1) to 17 mumol X kg-1 X min-1 while the total Ca content increased by 95 mumol X kg-1. This net Ca gain was reversed by 50 mM caffeine. As the external K+ was increased from 5 to 80 mM, the Bay K8644 stimulation of influx and contraction first increased and then decreased. The data are explained in terms of a calcium entry model consisting of membrane Ca2+ channels in series with a subplasmalemmal barrier consisting of superficial sarcoplasmic reticulum (SR).

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP98625264	(S)-(−)-Bay K8644		98625-26-4	Price

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