Endothelial nitric oxide synthase G894T gene polymorphism and response to skin reactive hyperemia

Post occlusive skin reactive hyperemia (PORH) is a tool used to assess microcirculation. Endothelial nitric oxide synthase (eNOS) mediates nitric oxide (NO) production; polymorphism of the eNOS gene may affect response to the PORH process. This study aims to determine whether eNOS G894T gene polymorphism affects response to skin PORH. 230 normotensive male and females between 18 and 40 years participated in this cross-sectional study. 170 subjects were of the homozygous GG genotype, whereas 60 were of the GT genotype. Skin PORH was performed by occlusion of the upper arm at 200 mm Hg for 3 min. Skin perfusion and temperature were monitored before, during and after occlusion release using the laser Doppler fluximetry. There were no significant differences between genotypes in their baseline blood pressure, serum cholesterol, BMI and age. Maximum change in perfusion after occlusion release (PORHmax) for the GG and GT genotypes were not significantly different at 50.15+/-1.29 vs. 47.92+/-2.17 AU; ANCOVA, p=0.351. Peak perfusion (PORHpeak) were also not significantly different between the two genotypes (61.23+/-1.36 vs. 57.72+/-2.32 AU; p=0.169). Minimum baseline perfusion were however higher in the GG compared to the GT genotype (10.83+/-0.29 vs. 9.61+/-0.50, p=0.029). We conclude that microvascular reactivity, assessed by change in perfusion after temporary ischemia was not significantly different between the GG and GT genotypes of the eNOS G894T gene. eNOS 894T allele carriers however, have lower baseline perfusion compared to the homozygous G894 allele carrier.