Key result
During 60° head-up tilt, young normotensive black women demonstrated significantly lower noradrenaline levels (267 vs 364 pg/ml) and muscle sympathetic nerve activity compared to white women.
Why the study?
Does orthostatic stress elicit different neural-humoral responses in healthy young black women compared to white women?
Cross-Sectional (n=25)
No
Does orthostatic stress elicit different neural-humoral responses in healthy young black women compared to white women?
Young normotensive white women may rely more on sympathetic neural activity, whereas black women tend to rely on the renal-adrenal system to regulate blood pressure during orthostatic stress.
Racial differences in orthostatic sympathetic activity may exist among young women; hypothesis-generating and should not yet change practice.
Young black women have higher prevalence of hypertension during pregnancy compared to white women, which may be attributable to differences in blood pressure (BP) regulation. We hypothesized that young normotensive black women would demonstrate augmented muscle sympathetic nerve activity (MSNA) and renal-adrenal responses to orthostasis. Fifteen white and ten black women (30 ± 4 vs. 32 ± 6 years; means ± SD) had haemodynamics and MSNA measured during baseline (BL), 30 and 60° head-up tilt (HUT), and recovery. Blood was drawn for catecholamines, direct renin, vasopressin, and aldosterone. BL brachial systolic BP (SBP: 107 ± 6 vs. 101 ± 9 mmHg) and diastolic BP (DBP: 62 ± 4 vs. 56 ± 7 mmHg) were higher in white women (both p < 0.05). Δ DBP (60° HUT-BL) was greater in black women compared to white (p < 0.05). Cardiac output and total peripheral resistance were similar between groups. MSNA burst frequency was higher in whites (BL: 16 ± 10 vs. 14 ± 9 bursts/min, main effect p < 0.05) and increased in both groups during HUT (60°: 39 ± 8 vs. 34 ± 13 bursts/min, p < 0.05 from BL). Noradrenaline was higher in white women during 60° HUT (60° HUT: 364 ± 102 vs. 267 ± 89 pg/ml, p < 0.05). Direct renin was higher and vasopressin and Δ aldosterone tended to be higher in blacks (BL, direct renin: 12.1 ± 5.0 vs. 14.4 ± 3.7 pg/ml, p < 0.05; BL, vasopressin: 0.4 ± 0.0 vs. 1.6 ± 3.6 pg/ml, p = 0.065; Δ aldosterone: -0.9 ± 5.1 vs. 3.8 ± 7.5 ng/ml; p = 0.069). These results suggest that young normotensive white women may rely on sympathetic neural activity more so than black women who have a tendency to rely on the renal-adrenal system to regulate BP during an orthostatic stress.
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Jarvis et al. (2014) conducted a cross-sectional in Healthy, normotensive (n=25). Black race vs. White race was evaluated on Noradrenaline concentration at 60° head-up tilt (pg/ml) (p=<0.05). During 60° head-up tilt, young normotensive black women demonstrated significantly lower noradrenaline levels (267 vs 364 pg/ml) and muscle sympathetic nerve activity compared to white women.
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