AJP - Heart and Circulatory Physiology, Vol 243, Issue 3 456-H462, Copyright © 1982 by American Physiological Society
Vasodepressor action of angiotensin in conscious chickens
Y. Nakamura, H. Nishimura and M. C. Khosla
In chronically cannulated conscious chickens, Gallus gallus, native chicken
angiotensin II ([Asp1,Val5]ANG II) caused biphasic blood pressure
responses, a depressor followed by a pressor response. The pressor response
appears to be mediated primarily by catecholamines. The depressor responses
increased with increasing doses and were accompanied by tachycardia. The
onset of the depressor action of [Asp1,Val5]ANG II (2.49 +/- 0.22 s) was
nearly as quick as that of acetylcholine or histamine. Replacement of
aspartic acid in position 1 with sarcosine or asparagine reduced both
depressor and pressor potencies, whereas there was no difference either in
depressor or pressor potencies between [Asp1,Val5] and [Asp1,Ile5]ANG II.
The depressor response to [Asp1,Val5]ANG II was not inhibited by atropine,
a vasopressin antagonist, prostaglandin synthetase inhibitors,
methysergide, or propranolol but was blocked markedly by [Sar1, Ile8]ANG II
and partially by [Sar1,Thr8]ANG II. The results suggest that the
vasodepressor action of ANG II is mediated by angiotensin receptors and may
possibly be a direct action on the vascular smooth muscle.
