Cardiac actions of bovine parathyroid hormone fragment (1-34) in some lower vertebrates.
Only recently have the cardiac actions of parathyroid hormone and its N-terminal (1-34) fragment (bPTH(1-34] been examined. Parathyroid hormone was found to exert a positive chronotropic effect on the heart tissue of several mammals and one amphibian in vivo and/or in vitro. The purpose of the present study was to examine in vitro the heart tissue of several lower vertebrates, particularly aquatic vertebrates, for responsiveness to bPTH(1-34) and, for comparative purposes, isoproterenol. Heart tissue (atrium or the entire heart) from all the animals studied (trout, mudpuppy, bullfrog tadpole, and adult bullfrog) responded to isoproterenol in a dose-dependent fashion with increased heart rate and contractile force. Only the atria from the adult bullfrog, however, responded in a similar manner to the administration of bPTH(1-34). In all cases propranalol (10(-6) M) was able to block both chronotropic and inotropic effects of isoproterenol but had no effect on the cardiac stimulation induced by bPTH(1-34) in the adult bullfrog atrium. The data suggests that cardiac responsiveness to bPTH(1-34) is associated with a terrestrial as opposed to an aquatic existence.
D000818:Animals; D002417:Cattle; D004305:Dose-Response Relationship, Drug; D006321:Heart / Q000187:drug effects*; D006339:Heart Rate / Q000187:drug effects; D007545:Isoproterenol / Q000494:pharmacology; D008675:Metamorphosis, Biological; D009200:Myocardial Contraction / Q000187:drug effects; D009337:Necturus / Q000502:physiology; D010281:Parathyroid Hormone / Q000494:pharmacology*; D010446:Peptide Fragments / Q000494:pharmacology*; D011433:Propranolol / Q000494:pharmacology; D011892:Rana catesbeiana / Q000502:physiology; D014337:Trout / Q000502:physiology
D010281:Parathyroid Hormone; D010446:Peptide Fragments; C025076:parathyroid hormone (1-34), bovine; D011433:Propranolol; D007545:Isoproterenol