β‐Adrenergic stimulation inhibits calcium efflux and alters the morphology of cultured arterial muscle cells

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Abstract
β‐Adrenoreceptor stimulation with isoproterenol (IP) rapidly and reversibly rounded and arborized smooth muscle cells (SMC) cultured from rat aorta. The arborized SMC remained firmly attached to the substratum via a network of long, dendritelike processes. Arborization of the SMC correlated closely with increases in cellular cAMP produced by IP and a variety of other compounds. The intracellular calcium antagonist 8‐(N,N‐diethylamino)‐octyl‐3,4,5‐trimethoxybenzoate (TMB‐8) also rounded and arborized the SMC. Antitubulin compounds potently blocked arborization by IP, dibutyryl cAMP, and TMB‐8. The release of cell‐bound 45Ca2+ was followed in the presence and absence of IP. IP strikingly increased the amount of 45Ca2+ that remained cell bound between 20 and 120 min Propranolol and colchicine prevented IP from inhibiting the release of cell‐bound 45Ca2+. These results suggest that the modulation of Ca2+ transport is involved in the arborization of cultured SMC by cAMP.