title: Relative contracting and relaxing potencies of a series of prostaglandins on isolated canine mesenteric artery strips.
abstract: The contracting and relaxing potencies of and interactions between a number of prostaglandins (PGs) were studied in vitro on spiral strips of small canine mesenteric arteries (outside diameter less than 1 mm). PGF2 alpha and PGE2, the most potent contracting PGs, were nearly equal in potency (EC50 4 x 10(-7) M) and did not cause relaxation under our experimental conditions. PGI2 and PGE1 were equal and the most potent relaxing PGs (EC50 3 x 10(-9) M). PGE1 also caused contraction, but this effect was not consistent. PGI2 did not cause contraction in concentrations up to 3 x 10(-6) M. In higher concentrations, however, it caused abrupt and near maximal contraction. PGD2 was weak in both respects, causing incomplete relaxation and contraction or biphasic effects. Interaction studies showed that PGE1 and PGI2 mutually excluded the relaxing effects of each other. PGE1 also reversed the relaxing effect of isoproterenol. However, pre-exposure to PGD2 did not attenuate the relaxing effect of PGE1 or PGI2 nor was the relaxing effect of PGD2 changed by pre-exposure to PGE1. Two different orders of potency of PGs suggest two PG receptors subserving contraction and relaxation, respectively. Further, it appears that several PGs can act upon both receptors which may explain unusual interactions between the PGs and some of their atypical effects. Finally, the data also suggest that there may be subtypes of the PG receptors subserving contraction and relaxation.
mesh_terms: D000818:Animals; D001681:Biological Assay; D004285:Dogs; D007545:Isoproterenol / Q000494:pharmacology; D008638:Mesenteric Arteries / Q000187:drug effects; D009119:Muscle Contraction / Q000187:drug effects*; D009126:Muscle Relaxation / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D009638:Norepinephrine / Q000494:pharmacology; D010646:Phentolamine / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D011453:Prostaglandins / Q000494:pharmacology*; D012977:Sodium Nitrite / Q000494:pharmacology
chemical_list: D011453:Prostaglandins; D011189:Potassium Chloride; D007545:Isoproterenol; D012977:Sodium Nitrite; D009638:Norepinephrine; D010646:Phentolamine