Blood pressure, heart rate and plasma renin activity at rest and during reactivity in black and white borderline hypertensive and normotensive males

Date of Award




Degree Name

Doctor of Philosophy (Ph.D.)


Black people in the U.S. have about twice the prevalence of hypertension as whites. In order to understand racial differences in blood pressure (BP) regulation that might contribute to the differential prevalence, BP, heart rate (HR) and plasma renin activity (PRA) at rest and during challenging behavioral tasks were evaluated. Participants were also assessed for 12-hr urinary sodium (Na) excretion. Subjects were 11 black (mean BP 136/91 mm Hg) and 17 white (132/92 mm Hg) untreated borderline hypertensive males who were compared with 26 black (121/73 mm Hg) and 22 white (120/72 mm Hg) normotensive males (mean age 33 years).Borderline hypertensives tended to be slightly older and heavier. Blood chemistries indicated that nonfasting blood Na levels were significantly higher in black borderline hypertensives and white normotensives relative to white hypertensive and black normotensive males. Triglycerides were markedly higher in white borderline hypertensives, and the ratio of low density to high density lipoprotein (LDL/HDL) was significantly greater for whites in general. At rest, in addition to BP differences, borderline hypertensives had higher HRs. Although normotensive blacks tended to have lower resting PRA values than whites, when hypertensives were considered, no significant group differences in resting PRA were noted. PRA values were not found to be associated with urinary NA excretion. Also, borderline hypertensives tended to excrete more urinary NA and K than normotensives, regardless of race.Race did not appear to mediate differences in responses to the various stressors, although during psychological challenge, hypertensive status was an important factor. No significant differences among groups in PRA response to either physical or psychological stress were noted, although PRA increased in response to both types of challenge for all subjects.Although emotional stress differentiated black and white hypertensives from normotensives, when reactivity was analyzed as a function of PRA or urinary Na excretion, the cold pressor test, which appears to increase BP by increasing peripheral resistance, best differentiated groups. Although differences in reactivity have previously been described between blacks and whites, the present study suggests that these may be attributable to differences in hypertensive status, Na excretion and/or PRA, rather than race per se. (Abstract shortened with permission of author.)


Psychology, Physiological

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