Genetic predisposition to hypertension and stress-induced alterations in heart rate

Abstract

Basal heart rates, obtained in the home cage, and heart rates obtained during restraint stress were compared in Dahl hypertension-sensitive (DS) and Dahl hypertension-resistant (DR) rats. Normotensive DS rats fed a low salt diet had lower basal heart rates than DR rats fed a low salt diet. DS rats made hypertensive by 3 weeks exposure to excess salt ingestion did not exhibit changes in basal heart rate. DR rats fed the high salt diet did not exhibit any elevations in either basal heart rate or blood pressure. Despite the lower basal rates of DS vis-á-vis DR rats, upon exposure to restraint, DS rats exhibited significantly greater increments in heart rate than diet matched DR rats throughout the 30-min restraint period. This difference is similar in direction to that observed in other experimental models of genetic hypertension and also similar to that observed when humans with a family history of hypertension are compared to controls. Hence, these results support the hypothesis that, despite different physiological and biochemical characteristics, a relatively high stress-induced increase in heart rate is a general distinguishing characteristic of organisms at high risk for hypertension.