Indexed on: 01 Apr '93Published on: 01 Apr '93Published in: Journal of Molecular and Cellular Cardiology
The effect of the alpha 1-adrenoceptor agonist phenylephrine (PE, 1-10 microM) and the beta-adrenoceptor agonist isoprenaline (ISO, 1-10 microM) on protein synthesis and ultrastructure of ventricular cardiomyocytes from adult rat in culture (6 days in medium 199 plus 20% fetal calf serum) was studied. In these cultures cardiomyocytes were spread, but not spontaneously contractile. ISO and PE significantly increased total cell protein and incorporation of (14C)-phenylalanine within 24 h of exposure. These effects were inhibited by the antagonists propranolol and prazosin, respectively. The incorporation of (14C)-uridine was stimulated only by PE but not ISO. Induction of fetal BB-isoform of cytosolic creatine kinase was also caused only by PE but not ISO. The ultrastructure of PE-treated cardiomyocytes was altered as compared to controls, by a greater number of Golgi complexes, denser myofibrillar structures and the appearance of paracrystalline bands in mitochondrial matrices. In conclusion, in this culture model the protein synthesis of cardiomyocytes can be stimulated, independently of the contractility, by either alpha 1- or beta-adrenoceptor agonists. Catecholamines differ, however, in their effects on specific cellular proteins and structures. Only alpha 1-adrenergic stimulation leads to a "fetal shift" in the expression of CK-isoforms.