Childhood familial and racial differences in physiologic and biochemical factors related to hypertension.

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Abstract
Early differences in hemodynamic variables and vasoactive substances between progeny of hypertensive and normotensive parents were sought in normotensive children aged 10-17 yr. Black (42) and white (34) children of hypertensive parents (cases) and an age-balanced group of 20 black and 45 white children of normotensive parents (controls) underwent exercise stress testing. Blood pressure, heart rate, urinary electrolytes, kallikrein, and prostaglandin E-like material, plasma renin activity and norepinephrine were measured before, during and after exercise. Analyses compared the findings of 4 subject groups: black cases with black controls, white cases with white controls, black cases with white cases and black controls with white controls. Based on family history of hypertension, significant familial differences were found. Black cases were larger (P = 0.003) when compared to black control subjects and had higher resting systolic, diastolic maximum exercise diastolic blood pressures and higher postexercise plasma renin activity (P = 0.04); white cases also were larger (P = 0.004) in comparison with white controls and had higher postexercise heart rates, higher preexercise urinary prostaglandin E-like material and lower plasma norepinephrine after exercise (P < 0.05). Significant racial differences were noted in heart rate, blood pressure, urinary electrolytes and other biochemical substances. Among the cases, black/white comparisons showed that blacks had lower postexercise heart rates, and higher resting and maximum exercise systolic and diastolic blood pressures (P < 0.04 for these comparisons). Blacks had higher preexercise urinary Na excretion, lower preexercise urinary K excretion (P < 0.003), and lower plasma renin activity before and after exercise (P < 0.003). Urinary kallikrein excretion before and after exercise was lower in blacks (P < 0.03). While blood pressures were similar among the black and white controls, comparisons revealed that the blacks had higher preexercise Na and K excretion (P < 0.005), lower plasma norepinephrine 10 min after exercise (P < 0.05). Significant intraracial and interracial differences in physiological and biochemical variables, thought to be related to the development of hypertensive diseases, were detected in normotensive children categorized according to a family history of hypertension. With use of these variables, the black case children can be separated from the other 3 groups and may have increased risk for the development of adult-onset hypertension.