The evaluation of the α-adrenoceptor blocking action of indoramin, phentolamine and thymoxamine on the rat and guinea-pig isolated mesenteric vasculature and aortic spiral preparations

Publisher Website
Google Scholar
Abstract
The perfused mesenteric vasculature of the rat is a specific, sensitive and stable preparation for the rapid determination of α-adrenoceptor blocking pA2 values. Both types of pA2 determination—the direct determination (Schild, 1947) and the Arunlakshana & Schild (1959) analysis—can be made on this tissue. Indoramin, phentolamine and thymoxamine were evaluated and gave respectively α-block pA2 values of 8̇05, 7̇84 and 6̇47. The pA2 values made on the rat perfused mesentery were compared with those obtained on the rat aorta (indoramin 7̇68, phentolamine 8̇29, thymoxamine 6̇50), the guinea-pig aorta (indoramin 7̇38, phentolamine 7̇64, thymoxamine 6̇93) and the perfused mesenteric bed of the guinea-pig (indoramin 8̇48, phentolamine 7̇51, thymoxamine 6̇97). Statistical analyses of Kb (dissociation constant) values suggest that indoramin has an additional blocking action on resistance vessels, which is not possessed by phentolamine or thymoxamine.