Cardiovascular effect of "peritoneal dialysate-depressor-I", a short-active hypotensive phospholipid in dog...

Cardiovascular action of "peritoneal dialysate-depressor-I" (PD.D-I), a short-acting hypotensive phospholipid occurring in dog peritoneal dialysate, was investigated. With an intravenous injection of PD.D-I into an anaesthetized rat, a sharp fall of arterial blood pressure was observed and the effects were dose dependent. The maximum hypotensive effect was about 60 mmHg and the minimum effective dose was approximately 35 micrograms/kg. Neither tachyphylaxis nor sensitization was observed. Even in conscious rats PD.D-I elicited hypotensive responses, though the effect was much weaker than that produced in anaesthetized rats. In spinal rats the hypotensive effects were also observed. In the tests on rats reserpinized or pretreated with antimuscarinic, antihistaminic, beta-adrenergic-blocking and ganglionic-blocking agents, the depressor effect of PD.D-I was not affected. PD.D-I elicited also hypotensive responses in anaesthetized cats, rabbits and guinea pigs in the same degree as those in anaesthetized rats. The relaxation of the peripheral blood vessels was observed in the test on perfused rabbit ear. The depressor factor showed no smooth muscle stimulating activity in isolated guinea pig ileum preparations. Judging from these findings, the hypotensive effect of PD.D-I is not ascribable to the central, sympathetic or parasympathetic nervous system but possibly to direct action on the peripheral vascular system.