Peripheral vascular resistance and regional blood flows in hypertensive Dahl rats.

The aim of this study was to determine whether different organs undergo similar increases in vascular resistance with hypertension in the Dahl salt-sensitive rat. Cardiac output and organ blood flows were measured with microspheres in anesthetized salt-sensitive and salt-resistant rats fed a high- (7%) or normal- (0.45%) salt diet for 4 wk. High salt intake produced hypertension only in salt-sensitive rats. Cardiac index for the hypertensive group was not different from that for any other group, whereas peripheral resistance index was elevated in proportion to arterial pressure. There were no differences among groups in the fraction of cardiac output supplying the myocardium, intestine, diaphragm, spinotrapezius muscle, or gracilis muscle. The fraction of cardiac output supplying the kidneys was lower in salt-sensitive rats (13%) than in salt-resistant rats (17%) and, among salt-sensitive rats, lowest in the high-salt group. Therefore all the organs studied contribute to increased total peripheral resistance in the hypertensive Dahl rat, with the renal vasculature undergoing the largest resistance increase. Different muscles undergo similar increases in vascular resistance, despite differences in the microvascular abnormalities accompanying salt-induced hypertension.