Biobehavioral Effects of Extended Salt Loading and Conflict Stress in Intact Baboons

Abstract

Behavioral stressors may inhibit sodium excretion, potentially increasing plasma volume and elevating blood pressure during chronic exposure. Blood pressure regulation may be especially deranged during manipulations that further challenge the kidney, such as a diet high in salt content. The effects on blood pressure and other variables of combined behavioral stress (food/shock conflict) and dietary salt (12 g NaCl per day; 218 mEq Na+ per day) were examined in adult male baboons over the course of 1 year. Mean arterial pressure was not significantly elevated over baseline after 5 months of high dietary salt alone (6 +/- 5 mmHg) but was maximally elevated by an average of 17 (+/- 3 SEM) mmHg after 5 months of combined salt and conflict stress. Control baboons showed no significant trends in mean arterial pressure across the same time period. Individual subjects whose blood pressure was "salt+stress resistant" or "salt+stress sensitive" were differentiated by their degree of pressure diuresis and natriuresis, urinary free cortisol, and a behavioral index of stress sensitivity. The data indicate additive effects of chronic high dietary salt intake and behavioral stressors on blood pressure in nonhuman primates that are dependent on renal function and pituitary-adrenocortical activity.

Interaction of Stress and Dietary NaCl Intake in Hypertension: Renal Neural Mechanisms

“…In the baboon the combined intervention of conflict stress and increased dietary NaCl intake resulted in an increase in mean arterial pressure (circa 15 mmHg) that was greater than that achieved with each separate intervention (circa 5 mmHg) (56)(57)(58).…”

Salt-Sensitivity and Other Predictors of Stress-Related Cardiovascular Reactivity in Healthy Young Males

“…Studies in humans (17), baboons (18), dogs (19) and rats (20,21) suggest that behavioral stress has an antinatriuretic effect, possibly mediated by increased renal sympathetic stimulation (21). Increased reactivity to mental stress could therefore be relevant for the pathogenesis of salt-sensitivity.…”