Calcium pools for noradrenaline and potassium-induced contractions of rat portal vein

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Abstract
The contractile responses of isolated normal and Ca-depleted rat portal veins to varying concentrations of noradrenaline (NA) and K+ have been studied with a view to further clarifying the sources of Ca for contraction using both agents. The comparably rapid times-to-peak of NA and K+ contractions of normal (Ca-containing) strips suggest mobilization of a common Ca pool, perhaps superficial; whereas, following Ca-depletion, NA appears to mobilize a superficial pool more readily than K+. Following K+ depolarization in Ca-free medium, NA produced a contraction sensitive to ryanodine, suggesting Ca release from an intracellular pool.