Vascular Smooth Muscle: Dual Effect of Calcium

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Science  15 Feb 1963:
Vol. 139, Issue 3555, pp. 597-599
DOI: 10.1126/science.139.3555.597


The first part of the contractile response of rabbit aorta to epinephrine is depressed by elevation of calcium concentration; the second is potentiated. These observations suggest that the rate-limiting factor for the former is membrane excitability (depressed by increased calcium), while that for the latter is the role that calcium plays in coupling membrane excitation with the development of tension by the contractile protein (a function that is augmented by increased calcium).

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