Alpha- and Beta-Adrenergic Stimulation of Protein Synthesis in Cultured Adult Ventricular Cardiomyocytes

The effect of the α₁-adrenoceptor agonist phenylephrine (PE, 1-10 μM) and the β-adrenoceptor agonist isoprenaline (ISO, 1-10 μM) 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 P.E. 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 hands in mitochondrial matrices. In conclusion, in this culture model protein synthesis of cardiomyocytes can be stimulated, independently of the contractility, by either α₁- or β-adrenoceptor agonists. Catecholamines differ, however, in their effects on specific cellular proteins and structures. Only α₁-adrenergic stimulation leads to a "fetal shift" in the expression of CK-isofoms.