The pressor actions of homologous kidney extract and human angiotensins I and II were studied in the conscious rat snake, Ptyas korros. A converting enzyme inhibitor (captopril), an angiotensin II analogue ([Sar1, Ala8]ANG II), an α-adrenergic receptor antagonist (phentolamine), and a catecholamine releaser (reserpine) were used to elucidate their actions. It was found that captopril attenuated the pressor effects of the kidney extract and angiotensin I but not that of angiotensin II. [Sar1, Ala8]ANG II and phentolamine both significantly attenuated, but did not completely inhibit the vasopressor actions of the kidney extract and angiotensins I and II. However, reserpine administration did not reduce the action of angiotensin II. These findings suggest that the renin-angiotensin system in snakes is similar to those present in mammals and other nonmammalian species, except for the mechanism of angiotensin II action. In the present study, angiotensin II was found to act partly through the α-adrenergic receptor which is not as specific as that in mammals and thus may respond to an agonist other than its usual ones, and partly through the vascular angiotensin II receptor.
ASJC Scopus subject areas
- Animal Science and Zoology