Physiological doses of [Ile5]- and [Val5]-Angiotensin II fail to increase plasma catecholamines at the peak pressor response in rats.
Pressor responses to [Ile5]-Angiotensin II and [Val5]-Angiotensin II were measured following single intravenous doses of 0.0075, 0.075, 0.375, 0.75 and 7.5 micrograms/kg b.w. in anesthetised rats. [Val5]-Angiotensin II was significantly (10 per cent) more potent than [Ile5]-angiotensin II when log dose was plotted against the increase in carotid arterial pressure. Doses of 0.075 microgram/kg b.w. or more of each of the two peptides gave a full pressor response within 30 seconds. However, only at the highest and, probably, nonphysiological dose of [Ile5]-Angiotensin II (7.5 micrograms/kg b.w.) was there a significant increase in noradrenaline and adrenaline concentrations measured using a radioenzymatic assay. [Val5]-Angiotensin II was more potent than [Ile5]-Angiotensin II insofar as plasma noradrenaline increased significantly (p < 0.05) following doses of 0.75 and 7.5 micrograms/kg b.w.; adrenaline at the higher dose only. Plasma dopamine was unresponsive to both peptides.
Department of Zoology, University of Toronto, Ramsay Wright Zoological Laboratories, Ontario, Canada.
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D000704:Analysis of Variance; D000804:Angiotensin II / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors* / Q000494:pharmacology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D002395:Catecholamines / Q000097:blood*; D004298:Dopamine / Q000097:blood; D004837:Epinephrine / Q000097:blood; D007275:Injections, Intravenous; D008297:Male; D009638:Norepinephrine / Q000097:blood; D051381:Rats; D017207:Rats, Sprague-Dawley; D012044:Regression Analysis
D002395:Catecholamines; D000804:Angiotensin II; C031193:angiotensin II, Asp(1)-Val(5)-; D004298:Dopamine; D009638:Norepinephrine; D004837:Epinephrine