CHARACTERISTICS OF INDIVIDUALS WHO EXCRETE VERSUS RETAIN SODIUM UNDERSTRESS

To examine the role of stress on renal sodium excretion, we studied 27 normotensive and 21 hypertensive subjects. All subjects were placed o n a standardized sodium diet. After water loading (2290 mi in 31/2 hr) they completed a 30 min baseline and a 30 min stress period (competit ive videogame). Sixty-nine percent of the subjects increased (''excret ers'') and 31% decreased (''retaimers'') their sodium excretion under stress. In addition to increased potassium excretion (p < 0.006), excr eters also manifested less of a stress associated increase in systolic (p = 0.055) and diastolic (p = 0.040) blood pressure and showed great er expression of anger (p < 0.02) than retainers. The same subjects we re also studied to determine the effects of angiotensin converting enz yme inhibition (captopril 25 mg b.i.d.) on sodium excretion. On captop ril, excreters now showed a retention of sodium (p < 0.001) and potass ium (p < 0.01) under stress and no longer differed significantly in bl ood pressure reactivity. The results suggest that there are two differ ent stress-related patterns of renal sodium excretion, that these patt erns are related to blood pressure responses to stress, and may be rel ated to anger expression. In addition, sodium excretion patterns under stress may be altered with certain type of antihypertensive medicatio ns.