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Greater orthostatic tolerance in young black compared to white women
Author(s) -
Hinds Kumba,
Stachenfeld Nina
Publication year - 2010
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.24.1_supplement.977.9
Subject(s) - presyncope , medicine , heart rate , baroreflex , blood pressure , endocrinology , orthostatic vital signs , plasma renin activity , renin–angiotensin system
We hypothesized that orthostatic tolerance (OT) is higher in young, healthy black (BW) compared to white women (WW). To determine OT, sixteen women (8 BW, 8 WW) underwent graded lower body negative pressure (LBNP) to presyncope. We measured blood pressure, heart rate, and R‐R interval (ECG) continuously at baseline and through all levels of LBNP. We took blood samples at baseline and presyncope for the measurement of plasma catecholamine and serum aldosterone concentrations and plasma renin activity. Cumulative stress index (CSI), the sum of the product of time and LBNP, was the indicator of OT. OT in the BW was ~ 50% greater than in the WW [CSI=−932.1 (402.1) vs. −496.9 (220.2) P < 0.05]. While P [NE] increased in both groups at presyncope, the increase was greater in BW [Δ P [NE] 171.0 (112.3)] versus WW [73.9 (70.9), P < 0.05], as were the increases in PRA [Δ PRA 2.6 (1.0) versus 0.6 (0.9) ng ANG II·ml −1 ·hr −1 , P < 0.05, for BW and WW, respectively). Although heart rate increased and R‐R interval decreased to a greater extent during LBNP in BW compared to WW [ANOVA, P < 0.05)], baroreflex function (i.e. slope R‐R interval vs. LBNP) was unaffected by race. These data indicate that OT is greater in black compared to white women, which appears to be a function of greater sympathetic nervous system responses orthostatic stress. HL071159