Hypotensive action of parathyroid hormone preparations on rats and dogs (synthetic parathyroid hormone/vasodilation/perfused kidney/perfused hindlimb/helical aorta strip)

Bovine parathyroid extract and two commer- cial preparations containing the first 34 amino acids of synthetic bovine parathyroid hormone IbPTH(1-34)) produced dose-re- lated hypotension in anesthetized rats. Dogs were 10 times more sensitive to the two bPTH(1-34) preparations than were rats. Propranolol, phentolamine, atropine, and promethazine did not affect the hypotensive action of bPTH41-34) in rats and dogs. bPTH(1-34) decreased perfusion pressure in rat hindlimbs perfused in situ with Ringer's solution and was a vasodilator in dog kidneys perfused in vitro with Ringer's solution. Helical strips of rabbit aorta were also relaxed by bPTH(1-34). We conclude that the direct vasodilatory action of bPTH prepara- tions represents an intrinsic property of parathyroid hormone and that the hypotensive effect of this hormone is produced by part or all of the first NH2-terminal 34 amino acids.