In vitro neurogenic and musculotropic responses to angiotensin peptides in normal and sodium-restricted rabbits.

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Abstract
Dietary Na restriction blunts pressor and accentuates steroidogenic responses to angiotensin II. The influence of dietary Na restriction on the myotropic and neurogenic responses to several angiotensin peptides was evaluated. Contractile responses to angiotensin II and III of aortic strips from rabbits on 4 days of Na restriction were depressed compared to responses in strips from control animals. Aortic contractions evoked by [Sar1]angiotensin II and serotonin were not influenced significantly by changes in dietary Na. Angiotensin II,[Sar1] angiotensin II and angiotensin III potentiated contractile responses of isolated rabbit vasa deferentia and portal veins to transmural stimulation without affecting contractions caused by norepinephrine. Potentiation of neurogenic responses by angiotensin II and III was depressed in portal veins from Na-restricted rabbits, whereas responses to [Sar1]angiotensin were variable. Potentiation of neurogenic responses by angiotensin peptides in the vas deferens was not influenced by changes in dietary na intake. The adrenergic response in portal vein, but not vas deferens is desensitized by 4 days of dietary Na restriction. The absence of change in responses to [Sar1]angiotensin II may indicate that accelerated angiotensin metabolism plays a role in the process of desensitization in vascular smooth muscle.