Abnormal renal hemodynamics and pressure-natriuresis relationship in Dahl salt-sensitive rats.

The renal responses to changes in renal perfusion pressure (RPP) were compared in Dahl salt-resistant (R) rats and in prehypertensive and hypertensive Dahl salt-sensitive (S) rats to determine whether an abnormality in the pressure diuresis response is involved in the development of this form of hypertension. Possible differences in the neural and endocrine background to the kidney of S and R rats were eliminated by denervating the kidney and by holding plasma levels of vasopressin, aldosterone, corticosterone, and norepinephrine fixed by intravenous infusion. Arterial pressure averaged 124 +/- 1 mmHg in R rats, 133 +/- 1 mmHg in prehypertensive S rats, and 158 +/- 2 mmHg in hypertensive S rats. Control renal blood flows (RBF) and glomerular filtration rates (GFR) were not significantly different in the three groups. RBF was autoregulated over a range of pressures from 80 to 160 mmHg in normotensive S and R rats. GFR was autoregulated at pressures greater than 100 mmHg in R rats and greater than 120 mmHg in prehypertensive S rats. In contrast, RBF was only autoregulated at pressures greater than 110 mmHg in hypertensive Dahl S rats, and GFR was significantly reduced from control when RPP was lowered below 150 mmHg. In R rats, increasing RPP from 100 to 150 mmHg produced a fivefold increase in urine flow and sodium excretion. In prehypertensive or hypertensive Dahl S rats the slopes of the relationships between urine flow, sodium excretion, and RPP were less than half of those seen in R rats.(ABSTRACT TRUNCATED AT 250 WORDS)