Classification of angiotensin receptors in rat isolated uterus, portal vein, and aorta with the novel competitive antagonist sarmesin.

Blockade of in vitro contractile responses to angiotensins II and III by the reversible competitive angiotensin antagonist [Sar1, Tyr(Me)4]ANG II (sarmesin) was investigated in 3 rat smooth muscle tissues. The pA2 values for sarmesin were: rat uterus, 7.46 +/- 0.04 versus ANG II and 7.46 +/- 0.07 versus ANG III; rat aorta, 7.98 +/- 0.07 versus ANG II and 7.67 +/- 0.08 versus ANG III; rat portal vein, 7.75 +/- 0.05 versus ANG II and 7.41 +/- 0.08 versus ANG III. Statistical analysis revealed that the pA2 values in each tissue were not significantly different, suggesting that ANG II and ANG III interact with the same receptors in each tissue. This conclusion was supported by cross-tachyphylaxis studies. Further statistical analysis revealed that pA2 values were not significantly different between tissues, suggesting that there are no readily discernible differences between angiotensin receptors in the 3 smooth muscle preparations investigated.