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New Findings What is the central question of this study? It is well recognized that there are disparities in cardiovascular disease outcomes between ethnic groups. Are there ethnic differences in microvascular function between healthy, young men and women of different ethnicities? This study used laser Doppler imagery and iontophoresis of acetylcholine and sodium nitroprusside to compare microvascular function between different ethnic groups and to understand the role of skin resistance in this methodology., What is the main finding and its importance? Endothelium-independent microvascular function remained attenuated after correcting for skin resistance in the Black African and mixed ancestry groups, suggesting that differences in smooth muscle function may be an important factor contributing to ethnic differences in disease risk., Microvascular dysfunction precedes the clinical manifestations of cardiovascular disease. Given the ethnic disparities in cardiovascular disease, we aimed to investigate ethnic differences in microvascular endothelial function in a group of young (18-33 years old), apparently healthy individuals ( n = 33, nine Black African, 12 mixed ancestry and 12 Caucasian). Microvascular endothelium-dependent and -independent function was assessed by laser Doppler imagery and iontophoresis of ACh and sodium nitroprusside (SNP), respectively, adjusting for skin resistance. Microvascular reactivity was expressed as maximum absolute perfusion, percentage change from baseline and area under the curve (AUC). Skin resistance was significantly lower in the Caucasian group in response to ACh (Caucasian, mean 0.16 ± 0.03 Ω versus Black, 0.21 ± 0.04 Ω and mixed ancestry, 0.20 ± 0.02 Ω, P < 0.01) and SNP (Caucasian, 0.08 ± 0.01 Ω versus Black, 0.11 ± 0.02 Ω and mixed ancestry, 0.12 ± 0.01 Ω, P < 0.01). Microvascular function in response to ACh was significantly higher in the Caucasian group compared with the other two groups; however, after adjusting for skin resistance these differences were no longer significant. Conversely, the microvascular SNP response remained significantly higher in the Caucasian group, even after adjusting for skin resistance ( P < 0.01). Diastolic blood pressure was inversely associated with the AUC of ACh ( r = −0.4) and all SNP responses ( r = −0.3 to −0.6). Skin resistance was inversely associated with AUC and maximum absolute ACh response ( r = −0.59 and −0.64, respectively) and all SNP responses ( r = −0.37 to −0.79). Ethnic differences in endothelium-independent microvascular function may contribute to ethnic disparities in cardiovascular disease. Moreover, skin resistance plays a significant role in the interpretation of the microvascular response to outcomes of iontophoresis in a multiethnic group. [ABSTRACT FROM AUTHOR]

Hormone replacement therapy (HRT) has been previously reported to modulate vascular function and cardiovascular risk. Its impact on the macrocirculation has previously been explored, however, little data is available on its impact on the microcirculation. This study aimed to determine the impact of HRT on microvascular function in healthy and Type 2 diabetic postmenopausal women (n = 20 and 17, respectively).Microvascular function was assessed by skin maximum hyperaemia, skin hyperaemic response to iontophoretically applied acetylcholine (endothelial-dependent vasodilator) and sodium nitroprusside (endothelial-independent vasodilator), capillary pressure and the microvascular filtration capacity. Microvascular assessments were carried out at baseline and repeated following 6 months’ oral hormone replacement therapy (1 mg oestradiol/0.5 mg norethisterone or 1 mg unopposed oestradiol for hysterectomized women).Following 6 months’ therapy there were no significant changes in microvascular assessments in the healthy women. In the diabetic women there was a reduction in the skin hyperaemic response to acetylcholine[median pretreatment peak response: 1.95 (25th, 75th centiles: 1.54, 2.30) V vs. post-treatment peak response: 1.53 (1.30, 1.91) V (P = 0.011, Wilcoxon's signed rank test)] and sodium nitroprusside[median peak response 1.59 (1.37, 1.99) vs. 1.35 (0.92, 1.63) V (P = 0.011)] with HRT, but no other changes.These data suggests that HRT does not affect microvascular function in healthy women, but adversely affects it in diabetic women. These findings may help to explain why HRT fails to provide the predicted cardiovascular protection, and raises the possibility that HRT influences microangiopathy progression in diabetic women.Diabet. Med. 22, 536–542 (2005) [ABSTRACT FROM AUTHOR]