title: Lack of specific inhibition of angiotensin II in eels by angiotensin antagonists.
abstract: Synthetic angiotensins I and II (AI and AII) and natural eel angiotensin were injected with angiotensin antagonists into freshwater-adapted, unanesthetized American eels, Anguilla rostrata, in an attempt to characterize the vasopressor properties of angiotensins in a primitive vertebrate. A converting enzyme inhibitor, SQ 20,881, inhibited vasopressor responses to eel angiotensin (presumably AI) and [Val5,Ser9]AI, but not those to [Asn1,Val5]AII, suggesting that a converting enzyme-like substance may exist in eels. [Sar1,Thr8]AII (10 microgram/kg per min) and [Sar1,Ile8]AII (1 microgram/kg per min), which antagonize angiotensin's action in mammals, showed neither agonistic vasopressor nor antagonistic effects in eels against [Asn1,Val5]AII or eel angiotensin. [Tal8]AII ([8-thienylalanine]AII) and a higher dose of [Sar1,Ile8]AII increased eel aortic pressure themselves and reduced vasopressor responses to [Asn1,Val5]AII. This is presumably a nonspecific decrease in response during the agonistic phase of the analogs. Angiotensin receptors in the blood vessels of eels may differ from those in mammals. Alpha-adrenergic blocking drugs and reserpine partially inhibited the pressor effect of [Asn1,Val5]AII in eels.
mesh_terms: D000803:Angiotensin I / Q000037:antagonists & inhibitors / Q000494:pharmacology; D000804:Angiotensin II / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D057911:Angiotensin Receptor Antagonists; D000818:Animals; D001794:Blood Pressure; D004305:Dose-Response Relationship, Drug; D004524:Eels / Q000502:physiology*; D005260:Female; D009638:Norepinephrine / Q000494:pharmacology; D010646:Phentolamine / Q000494:pharmacology; D051381:Rats; D011945:Receptors, Angiotensin / Q000502:physiology; D012504:Saralasin / Q000494:pharmacology; D013045:Species Specificity; D013722:Teprotide / Q000494:pharmacology; D014666:Vasomotor System / Q000187:drug effects*
chemical_list: D057911:Angiotensin Receptor Antagonists; D011945:Receptors, Angiotensin; D000804:Angiotensin II; D000803:Angiotensin I; D013722:Teprotide; D012504:Saralasin; D009638:Norepinephrine; D010646:Phentolamine