dinoprost and adenosine-3--5--cyclic-phosphorothioate

The role of endogenous prostaglandin production in phorbol diester-induced myocardial atrial natriuretic peptide (ANP) secretion was investigated in cultured spontaneously beating ventricular rat cardiomyocytes. Incubation of cells with 4 beta-phorbol 12-myristate 13-acetate (PMA; 0.1 microM) led to a rapid response in ANP release, a response accompanied by increases in cellular prostacyclin (PGI2) production, cyclic AMP (cAMP) formation and spontaneous contraction frequency. Although PMA-induced ANP secretion exhibited the pharmacological profile of a protein kinase C (PKC)-mediated event, the response was abolished in the presence of the cyclo-oxygenase inhibitors indomethacin (10 microM) and diclofenac (1 microM), indicating that endogenous prostaglandin production is responsible for PMA-induced ANP secretion in this system. Confirming this, PMA-induced ANP secretion was strongly correlated with endogenous formation of 6-oxo-prostaglandin F1 alpha (r = 0.93, P < 0.0005, n = 11), and exogenously applied PGI2, prostaglandin E2 (PGE2) or prostaglandin F2 alpha (PGF2 alpha) elicited simultaneous increases in cAMP formation, contraction frequency and ANP secretion in these cells. Furthermore, PMA-induced cAMP formation was abolished in the presence of either diclofenac or indomethacin, whereas the cAMP-elevating agent forskolin (0.1 microM) mimicked the secretory and chronotropic effect of PMA in these cells. A role for cAMP in PMA-induced ANP secretion was also apparent insofar as PMA-induced ANP release was substantially decreased in the presence of the Rp-diastereomer of 3',5'-cyclic adenosine monophosphorothioate (Rp-cAMPS; 10 microM), whereas the cAMP-mimetic agent dibutyryl cAMP (10 microM) provoked a rapid increase in ANP secretion in this system. Finally, the Ca(2+)-channel antagonist nifedipine (0.1 microM) severely decreased PGI2-, PGE2- and PMA-induced ANP secretion without affecting PGF2 alpha-induced peptide release, suggesting that PGI2 and/or PGE2, but not PGF2 alpha, are the prostanoids involved in PMA-induced ANP release. Taken together, these results suggest that PKC activation induces ANP secretion in spontaneously beating rat ventricular cardiomyocytes via an autocrine pathway involving increased PGI2 and/or PGE2 formation, a response leading to the activation of a myocardial adenylate cyclase and, subsequently, to that of a nifedipine-sensitive Ca2+ channel.

Topics: 6-Ketoprostaglandin F1 alpha; Animals; Animals, Newborn; Atrial Natriuretic Factor; Bucladesine; Cells, Cultured; Cyclic AMP; Diclofenac; Dinoprost; Dinoprostone; Epoprostenol; Heart; Heart Ventricles; Indomethacin; Kinetics; Myocardial Contraction; Myocardium; Nifedipine; Prostaglandins; Protein Kinase C; Rats; Rats, Wistar; Tetradecanoylphorbol Acetate; Thionucleotides

Two agents known to enhance the level of intracellular cAMP (dibutyryl cAMP and forskolin) markedly increase the number of 8.5, 10.5, and 11.5 days postcoitum (dpc) mouse primordial germ cells (PGCs) cultured on TM4 cell feeder layers. Forskolin (FRSK) caused a significant increase of PGC number also in monodispersed cell suspensions obtained from PGC-containing tissues of the three embryonic ages studied and in purified 11.5 dpc PGCs cultured without feeder layers. The addition to the culture medium of adenosine-3',5'-cyclic monophosphorothioate RP isomer (Rp-cAMPS, a competitive antagonist for cAMP-dependent protein kinases), significantly reduced the effects of FRSK. Last, FRSK stimulated PGC proliferation, as assessed by 5-bromo-2'-deoxyuridine incorporation. We conclude that cAMP-dependent mechanisms play a crucial role in the control of mitotic proliferation of mouse PGCs in culture.

Topics: Adrenocorticotropic Hormone; Animals; Bucladesine; Cell Division; Cells, Cultured; Colforsin; Cyclic AMP; Dinoprost; Dinoprostone; Embryo, Mammalian; Germ Cells; Kinetics; Mice; Protein Kinase Inhibitors; Thionucleotides; Time Factors