EFFECTS OF CATECHOLAMINES ON PROTEIN-SYNTHESIS IN CARDIAC MYOCYTES AND PERFUSED HEARTS ISOLATED FROM ADULT-RATS - STIMULATION OF TRANSLATION IS MEDIATED THROUGH THE ALPHA-1-ADRENOCEPTOR

Protein-synthesis rates in freshly isolated cardiac myocytes from adult rats were acutely stimulated by 20-30% by 1 μM-adrenaline, by 1 μM-noradrenaline or by 1 μM-phenylephrine, but were not stimulated by 1 μM-isoprenaline. Stimulation by 1 μM-adrenaline was completely prevented by 100 nM-prazosin. Yohimbine was much less effective in preventing stimulation, and 20 μM-DL-propranolol was completely ineffective. The stimulation of protein synthesis by adrenaline was still observed after inhibition of transcription by actinomycin D. None of these manipulations affected myocyte ATP contents. In anterogradely perfused hearts, protein-synthesis rates were stimulated by 1-2 μM-adrenaline in the presence of 10 μM-DL-propranolol (to decrease the β-adrenergic effects of adrenaline). ATP contents were not altered, but phosphocreatine contents were increased. These observations lead us to conclude that cardiac protein synthesis can be stimulated acutely at the level of translation by α1-adrenergic stimulation. We discuss possible roles for protein kinase C and intracellular alkalinization in the mediation of this effect.