Abstract
Studies have shown an increase in nitric oxide (NO) production during and following acute aerobic exercise (AAEX). In vitro studies indicate that eNOS gene polymorphisms (G894T and T-786C) may affect NO production. PURPOSE: To determine whether AAEX affects 24-hr urinary excretion rate of nitric oxide metabolites (NOx) and to investigate the possible association between the G894T and the T-786C eNOS gene polymorphisms and urinary NOx excretion rate following AAEX in African Americans with mild hypertension (SBP 145 ± 6 mmHg, DBP 85 ± 10 mmHg). METHODS: Seventeen (12 female, 5 male) sedentary, moderately obese (BMI 31.4 ± 5.7 kg/m2) subjects (mean age 58 ± 4) performed 50 min of AAEX at 65% VO2max. Urine was collected during 5 time periods (8:00-12:00, 16:00-20:00, 20:00-0:00, 0:00-8:00) before and after AAEX. NOx concentrations were determined using the Griess reaction and spectrophotometry. DNA was typed for the eNOS G894T and T-786C polymorphisms using standard PCR methods. Genotyping resulted in the following groups: G894T; GG (n = 12), GT (n = 5) and T-786C; TT (n = 14), TC+CC (n = 3). RESULTS: The NOx excretion rate during the 24-hr period following AAEX was not different from baseline (p = .34). However, excluding the sleeping hours (0:00-8:00), there was a trend for NOx excretion rate to be higher after AAEX (5.4 ± 1 vs 10 ± 2 mmol/hr, p = .06). Following AAEX, the T-786C TT genotype group had a greater average NOx excretion rate compared to the TC+CC genotype group (9.0 ± 2.1 vs 3.2 ± 0.8 mmol/hr, p = .07), while the G894T polymorphism showed no association with NOx excretion rate. CONCLUSION: These preliminary results suggest that AAEX increases daytime NO production and that the -786C allele may be associated with a blunted NO response to AAEX in hypertensive African Americans. Supported by American Heart Association-Mid Atlantic Affiliate Grant #99603164
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