Parental history of hypertension, sodium loading, and cardiovascular response to stress.

Parental history of hypertension, dietary sodium, and psychological stress have all been implicated in the development of essential hypertension and may interact in elevating disease risk. The mechanism by which this might occur is unclear, but it may be related to changes in the peripheral vasculature. The present study examined the effects of parental history and sodium on cardiovascular responses to an extended stressor. Eighteen normotensive offspring of hypertensives and 18 offspring of normotensives were exposed to a 1-hour shock-avoidance video-game procedure after 14 days of sodium loading (10 1-g tablets/day) and again after 14 days of placebo tablets. Order of sessions was counterbalanced between subjects in a double-blind design. In offspring of hypertensives, sodium loading elevated total peripheral resistance and norepinephrine responses to stress relative to placebo conditions and compared with offspring of normotensives. These increases were accompanied by decreases in stroke volume and cardiac output, which may explain the absence of familial differences in blood pressure responses to stress and sodium. Sodium loading had no effect on offspring of normotensives. The elevated resistance in offspring of hypertensives may suggest the initiation of pathological processes. The absence of sodium effects on resting values indicates the importance of research under conditions of stress.