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Title: Presença do polimorfismo 894G>T da óxido nítrico sintase endotelial altera as respostas hemodinâmicas durante o estressemental realizado após um exercício dinâmico máximo
Other Titles: Presence of the 894G>T polymorphism of endothelial nitric oxide synthase modifies the hemodynamic responses to a mental stress challenge performed after dynamic exercise
Keywords: Polimorfismo;  Estresse mental;  Reatividade vascular;  Exercício;  Polymorphism;  Mental stress;  Vascular reactivity;  Exercise;  MEDICINA;  CARDIOLOGIA;  Doenças cardiovasculares;  Estresse psicológico;  Óxido nítrico
Issue Date: 17-Mar-2010
Abstract: Nitric oxide (NO) is a key mediator of vasodilation during mental stress and to a variable extent also during dynamic exercise. Considering that genetic polymorphisms in the nitric oxide synthase (eNOS) gene seem to restrict the production of NO, this study aimed to evaluate the effects of the 894G>T eNOS polymorphism located in exon 7 on the hemodynamic responses to mental stress, before and after a bout of maximal dynamic exercise. Thirty-five healthy subjects were enrolled (32 ± 9 years, 80% women), 16 without (wild group; genotype GG) and 19 with the 894G>T polymorphism (polymorphic group, GT or TT genotype). The mental stress challenge consisted of the word-color conflict (Stroop color word test) before and 60 min after a maximal cardiopulmonary exercise test (CPET) performed on a treadmill following an individualized ramp protocol, designed to reach peak effort between 8-12 minutes. During mental stress, blood pressure was measured by the auscultatory method, heart rate was measured by a frequency counter and forearm vascular reactivity by the venous occlusion plethysmography. Forearm vascular conductance was derived from the ratio between forearm blood flow and mean arterial pressure. All measurements were performed in a double blind manner. The wild and polymorphic groups were similar regarding anthropometric, metabolic, resting blood pressure and CPET variables (P > 0.05). The genotypic proportions were in Hardy-Weinberg equilibrium (P > 0.05). Before the CPET, the systolic blood pressure response during mental stress was higher in the polymorphic group (&#916; wild group: 5.1 ± 2.0% vs. &#916; polymorphic group: 11.2 ± 1.8%, P = 0.04), while the vascular conductance increase was similar between the groups (&#916; wild group: 68.9 ± 22.1% vs. &#916; polymorphic group: 57.8 ± 20.1%, P = 0.46). After the CPET, systolic blood pressure at baseline and during mental stress was lower when compared to the measurement before the CPET (P < 0.05), regardless of the genotype. However, the systolic blood pressure response during mental stress was still higher in the polymorphic group (&#916; wild group: 3.6 ± 1.6% vs. &#916; polymorphic group: 8.9 ± 1.4%, P= 0.04). The vascular conductance response during mental stress was lower in polymorphic group when compared to the measurement before the CPET (&#916; polymorphic group before the CPET: 57.8 ± 20.1% vs. &#916; polymorphic group after the CPET: 21.0 ± 12.9%, P = 0.03). The diastolic blood pressure and heart rate responses to mental stress were similar between the groups before and after the CPET (P > 0.05). Thus, it appears that subjects with the polymorphism 894G>T presented a higher blood pressure increase in response to mental stress, both before and after a maximal bout of dynamic exercise, and a blunted vascular conductance response after exercise
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