Chronotropic actions of bPTH-(1-34) in the right atrium of the rat.
Bovine parathyroid hormone and its N-terminal (1-34) peptide fragment (bPTH-(1-34] are known to possess direct hypotensive activity in the rat. The purpose of the present study was to determine if bPTH-(1-34) possessed a direct chronotropic action as well. In vivo studies revealed that bPTH-(1-34) did produce a chronotropic effect in the rat comprising both a direct component as well as a reflex tachycardia related to its hypotensive actions. In vitro studies of isolated right atria indicated that while bPTH-(1-34) had no positive inotropic effect, it did produce significant chronotropic effects which were direct and dose-dependent. The potency of bPTH-(1-34) was found to be similar to that of isoproterenol, however, it was only one-third as effective as isoproterenol in maximally increasing atrial rate. A slight but significant increase in atrial cyclic AMP was generated prior to the chronotropic actions of bPTH-(1-34).
D000320:Adrenergic Fibers / Q000502:physiology; D000818:Animals; D000242:Cyclic AMP / Q000502:physiology; D006321:Heart / Q000187:drug effects*; D006339:Heart Rate / Q000187:drug effects*; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D010281:Parathyroid Hormone / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D012110:Reserpine / Q000494:pharmacology
D010281:Parathyroid Hormone; D012110:Reserpine; D011433:Propranolol; D000242:Cyclic AMP; D007545:Isoproterenol