Comparison of the potencies of some prostaglandins as vasodilators in three vascular beds of the anaesthetised dog.

Following close intra-arterial administration to the carotid and femoral arterial beds of the anaesthetised dog the rank order of potency for producing vasodilation was PGE greater than 11-deoxy PGE0 greater than PGA greater than PGI2 greater than PGB with the 1- and 2-series prostaglandins equipotent. PGI2 was about 60 times weaker than PGE1. In the mesenteric arterial bed the rank order of potency for producing vasodilation was the same except PGI2 was about equipotent with PGE1. The absolute potency of the prostaglandins, with the exception of PGI, was similar on all three vascular beds. A similar differential action of PGI2 relative to PGE1 was also observed following both left intraventricular and intravenous administration. We suggest that all three arterial beds contain PGE-receptors mediating vasodilatation at which the E-series prostaglandins are potent and PGI2 is weak. In addition the mesenteric bed contains PGI2-receptors which are absent or sparse in the carotid and femoral beds.