Cardiovascular and renal responses to stress in borderline hypertensive rat.

Wistar-Kyoto (WKY) and borderline hypertensive rats (BHR) were exposed to either a normal or high-sodium chloride (NaCl) diet for 8 wk. Cardiovascular and renal data were collected from arterial and bladder catheters, respectively, in conscious animals during control and stress (aversive classical conditioning) sessions. Results indicated that BHR on a high-NaCl diet exhibited no increase in blood pressure in response to stress compared with BHR on a normal diet. A high-NaCl diet diminished the recovery of blood pressure to base line during stress in WKY compared with normal NaCl controls. Also, a high-NaCl diet and stress interacted in the BHR to decrease sodium excretion and renal plasma flow during stress compared with the control session (3.8 vs. 4.8 mueq.min-1.100 g body wt-1; 3.6 vs. 4.0 ml.min-1. 100 g body wt-1, respectively). Finally, increased dietary NaCl blunted the norepinephrine response to stress in WKY but not in BHR (263 vs. 767 pg/ml). These data suggest that the interaction of genetic and environmental factors are important variables for the development of hypertension.