Trophic Effects of Catecholamines and Parathyroid Hormone on Adult Ventricular Cardiomyocytes

Trophic effects of isoproterenol (Iso), norepinephrine (NE), phenylephrine (PE), and biologically active fragments of parathyroid hormone (PTH), PTH-(1-34) and PTH-(28-48), were investigated in mechanically quiescent, isolated ventricular cardiomyocytes from adult rat. In 24-h incubations in modified serum-free medium 199 incorporation of [14C]phenylalanine, changes in total protein and specific activities of cytosolic enzymes, creatine kinase (CK) and lactate dehydrogenase (LDH) were monitored. NE and PE (10 microM), but not Iso, distinctly increased phenylalanine incorporation, total cell protein, and specific activity of CK but not LDH. Induction of CK, but not LDH, was also produced by phorbol 12-myristate 13-acetate (10 nM) but not dibutyryl adenosine 3',5'-cyclic monophosphate (DBcAMP, 1 mM). It was abolished by copresence of cycloheximide (35 microM) or actinomycin D (5 microM). CK-BB was the only induced isoform of CK, as shown for PE incubations. PTH-(1-34) and PTH-(28-48) (30-300 nM) had effects comparable to NE and PE. They increased phenylalanine incorporation and total protein content and induced CK but not LDH. In summary, distinct trophic effects on adult cardiomyocytes were found with alpha 1-adrenergic agonists, fragments of PTH containing the midregional amino acids 28-34, and direct activation of protein kinase C but neither beta-adrenergic agonists nor DBcAMP.