Cardiovascular effects of parathyroid hormone in the frog,Rana catesbeiana

Summary Mean arterial blood pressure ( ), heart rate (HR), and cardiac isometric contractile force (CF) were recorded simultaneously in the anesthetized frog,Rana catesbeiana, and the effects of the synthetic 1–34 peptide of bovine parathyroid hormone, bPTH-(1-34), on these cardiovascular parameters were tested. Doses of 10, 20, 40, 80, and 100 U·kg^–1 of PTH were administered i.v. and the effects noted. Isotonic (frog) saline was used as control. Following bPTH-(1-34), decreased in dose-dependent fashion, reaching maximum within 60 s post-injection with a duration of 7–8 min. CF was shown for the first time to decrease in dose-dependent fashion, reaching a maximum within 70 s and exhibiting a duration of approximately 8 min. No effect of bPTH-(1-34) on heart rate was noted.Abbreviations bPTH-(1-34) 1-34 peptide of bovine parathyroid hormone - mean arterial pressure - HR heart rate - CF cardiac contractile force - U international units - SR sarcoplasmic reticulum