Parasympathetic reactivation after a cardiopulmonary exercise test in humans is not associated with the endothelial nitric oxide synthase gene polymorphisms

      Nitric oxide (NO) plays a role on parasympathetic reactivation after a maximal exercise test. Previous studies have shown that endothelial nitric oxide synthase (NOS3) gene polymorphisms reduce NO bioavailability. Therefore subjects with NOS3 polymorphisms may have lower parasympathetic reactivation after exercise. The aim of this study was to investigate the influence of three NOS3 gene polymorphisms (−786T>C, intron 4b4a and 894G>T) on parasympathetic reactivation within the first 5 min after a maximal cardiopulmonary exercise test. The study included 139 healthy, sedentary and non-smokers volunteers (109 women/30 men, age 32±15 years, body mass index 25.8±5.5 kg/m2). Subjects were genotyped through polymerase chain reaction and restriction length polymorphism reactions, and were analyzed in groups according to the absence [wild-type (WT)] or the presence of at least one polymorphic allele [polymorphic-type (PT)] for each polymorphism. The parasympathetic reactivation was assessed by heart rate (HR) recovery (HRR) and variability (HRV). HRR was analyzed as the absolute HR decay at 1, 3 and 5 min during recovery compared with the peak HR (Δ1 min, Δ3 min and Δ5 min) and also as the kinetics of HRR (Tau: time elapsed to obtain 63% of the response). HRV was analyzed by the root mean square of successive beats differences (RMSSD) using 30-second windows. There was no difference for Δ1 min between WT and PT groups regarding the polymorphisms -786T>C (WT: 22±1 vs. PT: 22±1 bpm, p=0.91), intron 4b4a (WT: 22±1 vs. PT: 22±1 bpm, p=0.98) and 894G>T (WT: 22±1 vs. PT: 22±1 bpm, p=0.73). Similar results were found for Tau [−786T>C (WT: 2.6±0.2 vs. PT: 2.6±0.2 min, p=0.95); intron 4b4a (WT: 2.7±0.2 vs. PT: 2.3±0.2 min, p=0.24); 894G>T (WT: 2.6±0.2 vs. PT: 2.6±0.3 min, p=0.90)] and for other HRR and HRV variables. In conclusion, these results refute the hypothesis that the presence of NOS3 polymorphisms could reduce the parasympathetic reactivation after a maximal exercise test.
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