EFFECTS OF ENOS GENE POLYMORPHISM ON 24-HOUR URINARY NITRIC OXIDE METABOLITE LEVELS AFTER ACUTE EXERCISE

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