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1.
Am J Physiol Endocrinol Metab ; 286(1): E20-4, 2004 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-12954599

RESUMO

High-altitude exposure changes the distribution of body water and electrolytes. Arginine vasopressin (AVP) may influence these alterations. The purpose of this study was to examine the effect of a 24-h water deprivation trial (WDT) on AVP release after differing altitude exposures. Seven healthy males (age 22 +/- 1 yr, height 176 +/- 2 cm, mass 75.3 +/- 1.8 kg) completed three WDTs: at sea level (SL), after acute altitude exposure (2 days) to 4,300 m (AA), and after prolonged altitude exposure (20 days) to 4,300 m (PA). Body mass, standing and supine blood pressures, plasma osmolality (Posm), and plasma AVP (PAVP) were measured at 0, 12, 16, and 24 h of each WDT. Urine volume was measured at each void throughout testing. Baseline Posm increased from SL to altitude (SL 291.7 +/- 0.8 mosmol/kgH2O, AA 299.6 +/- 2.2 mosmol/kgH2O, PA 302.3 +/- 1.5 mosmol/kgH2O, P < 0.05); however, baseline PAVP measurements were similar. Despite similar Posm values, the maximal PAVP response during the WDT (at 16 h) was greater at altitude than at SL (SL 1.7 +/- 0.5 pg/ml, AA 6.4 +/- 0.7 pg/ml, PA 8.7 +/- 0.9 pg/ml, P < 0.05). In conclusion, hypoxia appeared to alter AVP regulation by raising the osmotic threshold and increasing AVP responsiveness above that threshold.


Assuntos
Altitude , Arginina Vasopressina/sangue , Privação de Água/fisiologia , Equilíbrio Hidroeletrolítico/fisiologia , Adulto , Humanos , Masculino , Concentração Osmolar
2.
Med Sci Sports Exerc ; 33(11): 1855-61, 2001 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-11689735

RESUMO

PURPOSE: Despite the widespread belief that endurance exercise lowers blood pressure (BP), reports of the lack of such an effect are common when using ambulatory blood pressure (ABP) monitoring. This review examined the influence of dynamic exercise on ABP to elucidate possible reasons for conflicting reports. METHODS: Criteria for inclusion were dynamic exercise studies that involved ABP determinations after exercise. A total of 23 studies containing 34 groups of which 12 were normotensive and 22 hypertensive met these criteria. The groups primarily consisted of unmedicated, sedentary, overweight, non-Hispanic white men and women with a mean +/- SEM age of 43.9 +/- 1.5 yr. RESULTS: Baseline mean day systolic BP (SBP) was 137.3 +/- 2.1 mm Hg (95% confidence limits) (133.0, 141.5) and diastolic BP (DBP) was 86.7 +/- 1.5 mm Hg (83.7, 89.7). After exercise, day SBP (N = 34) was reduced an average of 3.2 +/- 1.0 (-5.2, -1.2) (P = 0.003) and DBP by 1.6 +/- 0.6 mm Hg (-2.9, -0.4) (P = 0.013); night SBP (N = 20) by 3.4 +/- 1.0 (-5.6, -1.2) (P = 0.005) and DBP by 3.0 +/- 1.4 mm Hg (-5.6, -0.4) (P = 0.025); and 24-h SBP (N = 17) by 3.2 +/- 0.8 (-4.9, -1.6) (P = 0.001) and DBP by 1.8 +/- 0.5 mm Hg (-2.9, -0.7) (P = 0.003). After detection of outlying cases using regression diagnostics, initial SBP accounted for 30% (P = 0.001) and 26% (P = 0.018) of the variance in the change in day and night SBP after exercise, respectively. Similarly, initial DBP explained 37% (P = 0.000) and 33% (P = 0.005) of the difference in day and night DBP after exercise. CONCLUSION: The ABP difference after exercise is a function of initial values such that groups with the highest baseline BP experience the greatest postexercise ABP reductions. The ABP dynamic exercise studies raise important methodological considerations that should be attended to in future work.


Assuntos
Monitorização Ambulatorial da Pressão Arterial , Pressão Sanguínea/fisiologia , Exercício Físico/fisiologia , Adulto , Ritmo Circadiano/fisiologia , Feminino , Humanos , Hipertensão/fisiopatologia , Masculino , Pessoa de Meia-Idade , Valores de Referência , Análise de Regressão
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