The effect of hypertension, sodium, and race on isoproterenol sensitivity

The heart rate response to isoproterenol is felt to be an index of beta receptor sensitivity. We studied this response in 55 normotensive and mildly hypertensive men on two dietary salt intakes (10 meq sodium per day, and 200 meq sodium per day). There was no relationship between receptor functioning and diagnosis of hypertension. Similarly, age, relative body weight, and resting plasma catecholamines were unrelated to the heart rate response to isoproterenol. There was however, a significant three-way interaction between race, diagnosis, and dietary salt. Black hypertensives fail to down regulate their beta receptors' response to isoproterenol in the face of a high salt challenge (p less than .006).