Influence of dietary salt intake on the response of isolated perfused mesenteric veins of the dog to vasoactive agents

Background Previous work has established that a high dietary salt intake results in enhanced arterial vasoconstrictor responses to stimulation with agonists. This investigation was designed to investigate the effects of dietary salt on the responses of isolated capacitance vessels (third order mesenteric veins). Methods Dogs were fed diets containing low, intermediate, and high levels of dietary salt (0.4, 3.0, and 6.0 mmol kg/day). The animals were killed, and lengths of mesenteric vein were mounted in a perfusion myograph with changes in lumenal diameter measured using a video tracking device. Responses to cumulative doses of norepinephrine (NE) and acetylcholine (Ach) were then determined. Results The vasoconstrictor responses to NE were greater in the veins from dogs on a high salt diet. Acetylcholine also caused venoconstriction that also was greater in the high salt group of animals. Responses to Ach were unaffected by Nω-nitro-L-arginine methyl ester but were abolished by atropine. Conclusions These results indicate that mesenteric veins from dogs fed a high salt diet constrict more powerfully in response to agonists, which could contribute to the hypertensive effects of high intakes of dietary salt.