expression and cardiovascular physiology in the rainbow trout

doi:10.1152/ajpregu.00263.2006.—Experiments were conducted on rainbow trout to determine the impact of dietary salt on arterial blood pressure. After 4–6 wk, fish fed a salt-enriched diet exhibited a 37% elevation of dorsal aortic pressure (from 23.8 1.2 to 32.6 1.4 mmHg) and an 18 % increase in ventral aortic pressure (from 33.0 1.5 to 38.9 1.3 mmHg). The hypertension presumably reflected the increase in cardiac output (from 31.0 0.8 to 36.4 2.2 ml min1 kg1) because systemic and branchial resistances were statistically unaltered by salt feeding. The chronic hypertension was associated with a decrease in the pressor responses of the systemic vasculature to catecholamines and hypercapnia in the salt-fed fish. The reduction in -adrenergic responsiveness of the systemic vascu-lature is consistent with desensitization or loss of functional -adre-noceptors (-ARs). In support of this idea, the salt-fed fish exhibited significantly decreased levels of 1D-AR mRNA in the dorsal aort