Vasoactive properties of urotensins I and II in a columbiform and three galliform birds, and a bioassay for urotensin I

Summary Crude extracts ofGillichthys urophyses and chromatographically purified urotensin I (UI) and urotensin II (UII) (fromCatostomus urophyses) were injected intravenously intoCoturnix coturnix japonica, Colinus virginianus, Alectoris graeca (Galliformes) andColumba livia (Columbiformes). Changes in arterial blood pressure were monitored. UI elicited dose-dependent vasodepressor responses in all birds. Thioglycollate treatment abolished the depressor action of arginine vasotocin but not that of UI (in all birds). UII was a pressor agent inCoturnix andColinus, both members of the Galliformes. However, the hormone had no pressor activity inColumba, a member of the Columbiformes, and in another member of the Galliformes,Alectoris. The pressor effect of UII was also dose-dependent. Injection of crude urophysial extract intoColinus andCoturnix, therefore, elicited biphasic responses. UII effects can be abolished by prior incubation with carboxypeptidase A. Intravenous injection of the -adrenoceptor blocker, phenoxybenzamine, prior to urotensin injections had no effect on the responses to urotensins. As the chukar,Alectoris graeca, is sensitive to UI and resistant to anesthesia and surgery, and does not readily develop tachyphylaxis to repeated UI injections, its use is recommended as a routine bioassay animal for UI.