Cardiovascular effects of bPTH-(1-34) and isoproterenol in the frog, Rana tigrina.

1. The cardiovascular effects of bovine parathyroid hormone fragment [bPTH-(1-34)] and isoproterenol (ISO) on frog (Rana tigrina) isolated atria and helical strips of blood vessels were examined since PTH produces a beta-adrenergic-like effect in the mammal. 2. Data showed that both bPTH-(1-34) and ISO were vasorelaxant in KCl and arginine vasoctocin (AVT) preconstricted dorsal aorta, iliac and femoral arteries. 3. They both relaxed extracellular calcium-dependent contrations. 4. There was no additive nor synergistic effect between them in AVT preconstricted strips. 5. Both bPTH-(1-34) and ISO were positively inotropic but differed in their chronotropic effects, being negative and positive. 6. In the tiger frog, bPTH-(1-34) shows beta-adrenergic like contractile responses in both the cardiac and vascular smooth muscle as in the mammal, but not in the heart rate.