Effects of synthetic parathyroid hormone on hemodynamics and regional blood flows

In pentobarbital anesthetized dogs, synthetic bovine parathyroid hormone, containing the amino terminal 34 amino acids (bPTH-(1-34] in doses of 0.1-0.8 microgram/kg i.v. caused dose-related decrease in arterial blood pressure, increase in cardiac output and prominent reduction of total peripheral resistance. Marked increase of coeliac, coronary and renal blood flows and decrease of vascular resistances in these beds occurred. Mesenteric and iliac blood flows usually decreased. Changes in mesenteric resistance were minimal while iliac resistance increased substantially. The increase of renal blood flow was still obvious 10-20 min or longer after arterial blood pressure had returned to control levels. Mesenteric and iliac vasoconstriction were attributable to reflex increase in sympathetic activity since some decrease in resistances in these beds were seen in response to bPTH-(1-34) after ganglionic blockade. Renal vasodilation was not related to a prostaglandin mechanism as similar dilation occurred after prostaglandin synthesis inhibition with indomethacin. In summary, bPTH-(1-34) has prominant effects on the circulation, and does not affect all vascular beds similarly. The exact mechanism of the vasodilating action of bPTH remains to be elucidated.