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

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 45 Ca 2+ was followed in the presence and absence of IP. IP strikingly increased the amount of 45 Ca 2+ that remained cell bound between 20 and 120 min Propranolol and colchicine prevented IP from inhibiting the release of cell‐bound 45 Ca 2+ . These results suggest that the modulation of Ca 2+ transport is involved in the arborization of cultured SMC by cAMP.