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

Abstract

SUMMARY Early differences in hemodynamic variables and vasoactive substances between progeny of hypertensive and normotensive parents were sought in normotensive children aged 10-17 years. Forty-two black and 34 white 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 four subject groups: black cases with black controls, white cases with white controls, black cases with white cases, black controls with white controls. Based on a 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, dlastolic, and 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). Additionally, blacks had higher preexercise urinary sodium excretion, lower preexercise urinary potassium excretion (p < 0.003), and lower plasma renin activity before and after exercise (p < 0.003). Finally, urinary kallikrein excretion before and after exercise was lower in blacks (p < 0.03). While blood pressures were similar among the black and the white controls, comparisons revealed that the blacks had higher preexercise sodium and potassium excretion (p < 0.005), lower plasma renin activity at all levels of activity, and lower plasma norepinephrine 10 minutes after exercise (p < 0.05). Thus, significant intraracial and interracial differences in physiological and biochemical variables, thought to be related to the development of hypertensive diseases, have been 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 three groups and may have increased risk for the development of adult onset hypertension. 57Considerable information has been published concerning the familial aggregation of hypertension. Paffenbarger et al. 5 in 1968 reported that a parental history of hypertension was correlated with the development of the disorder in youths followed into later years. Familial aggregation of blood pressures through childhood was established by Zinneretal. 6 in 1971. ...

Why is plasma renin activity lower in populations of African origin?

“…Moreover, PRA distributions are not normal, although there is no evidence for a bimodal distribution in blacks. A lower plasma PRA has also been observed in some 10,17 but not in every study 18,19 of black children compared with white children, however, it is apparent that the difference between black and white children becomes more pronounced with increasing age even over an age range of 8-14 years. 17 Interestingly, slightly lower PRA has also been reported in black neonates.…”

Hypertension in developing nations in sub-Saharan Africa

“…30 Suppression of the renin-angiotensin system has been demonstrated. [31][32][33] We have found a higher plasma renin activity (PRA) in rural compared to urban Zulus. This suggests that the cause of a low PRA in black subjects may not be genetic.…”

Hypertension in black South Africans

“…12 Renin is lower in black people and does not increase in response to sodium and volume depletion. [13][14][15][16] The distribution curve of plasma renin in black Americans is not 'normal' but rather logarithmic, in contrast to the curve found in whites. 13 We have found that rural Zulus have higher plasma renin activity (PRA) compared to urban Zulus.…”