A comparison between the prostaglandin releasing effects of angiotensin II and angiotensin III.

Angiotensin II and its natural fragment (des-aspartic acid)1-angiotensin II (angiotensin III) induced a dose-dependent contraction in the isolated rat stomach fundus strip and rat colon. 1-Acetyl-2-(8-chloro-10,11-dihydrodibenz(b,f)(1,4)oxazepine-10, carbonyl) hydrazine (SC 19220), a widely used competitive-blocker of prostaglandins and acetyl salicylic acid, a well-known inhibitor of prostaglandin biosynthesis, partially abolished the contraction induced by both peptides in the rat stomach fundus but not in the rat colon. The inhibition induced by SC 19220 and acetyl salicylic acid was found to be higher for angiotensin III than angiotensin II when the dose-response curves and equipotent concentrations of the peptides were compared before and after the drugs. These results were taken as evidence that some component of the contractile effects of angiotensin II and angiotensin III on the isolated rat stomach fundus involves the release of prostaglandins by the peptides and in this respect angiotensin III has higher potency than angiotensin II.