ACTIVATION BY ALPHA(1)-ADRENERGIC AGONISTS OF THE PROGRESSION PHASE IN THE PROLIFERATION OF PRIMARY CULTURES OF SMOOTH-MUSCLE CELLS IN MOUSE AND RAT AORTA

The effects of catecholamines on the competence and progression phases in the proliferation of vascular smooth muscle cells (SMCs) in mouse and rat were investigated in primary cultures. alpha,beta-Adrenergic a gonists such as epinephrine and norepinephrine, and the alpha-adrenerg ic agonist, phenylephrine, stimulated proliferation of primary culture d SMCs, whereas the alpha(2)-adrenergic agonist, clonidine, and beta-a drenergic agonist, isoproterenol, did not. The stimulating effect of e pinephrine was maximal at 0.54 mu M and was then decreased at higher c oncentrations. The alpha-adrenergic antagonist, phentolamine, and alph a(1)-adrenergic antagonist, prazosin, inhibited epinephrine-induced SM C proliferation, while the alpha(2)-adrenergic antagonist, yohimbine, and beta-adrenergic antagonist, propranolol, did not. In primary cultu red and synchronized SMCs at the G(0) phase, norepinephrine accelerate d the rate of SMC proliferation, but did not change the starting time of DNA synthesis and proliferation. These results show that catecholam ines activate the progression phase in primary cultured aortic SMCs al pha(1),-adrenergic receptors.