Effect of gender on training-induced vascular remodeling in SHR

There is accumulating evidence that physical inactivity, associated with the modern sedentary lifestyle, is a major determinant of hypertension. It represents the most important modifiable risk factor for cardiovascular diseases, which are the leading cause of morbidity and mortality for both men and women. In addition to involving sympathetic overactivity that alters hemodynamic parameters, hypertension is accompanied by several abnormalities in the skeletal muscle circulation including vessel rarefaction and increased arteriole wall-to-lumen ratio, which contribute to increased total peripheral resistance. Low-intensity aerobic training is a promising tool for the prevention, treatment and control of high blood pressure, but its efficacy may differ between men and women and between male and female animals. This review focuses on peripheral training-induced adaptations that contribute to a blood pressure-lowering effect, with special attention to differential responses in male and female spontaneously hypertensive rats (SHR). Heart, diaphragm and skeletal muscle arterioles (but not kidney arterioles) undergo eutrophic outward remodeling in trained male SHR, which contributed to a reduction of peripheral resistance and to a pressure fall. In contrast, trained female SHR showed no change in arteriole wall-to-lumen ratio and no pressure fall. On the other hand, training-induced adaptive changes in capillaries and venules (increased density) were similar in male and female SHR, supporting a similar hyperemic response to exercise.

Time course of training-induced microcirculatory changes and of vegf expression in skeletal muscles of spontaneously hypertensive female rats

Exercise-induced vessel changes modulate arterial pressure (AP) in male spontaneously hypertensive rats (SHR). Vascular endothelial growth factor (VEGF) is important for angiogenesis of skeletal muscle. The present study evaluated the time course of VEGF and angiogenesis after short- and long-term exercise training of female SHR and Wistar Kyoto (WKY) rats, 8-9 weeks (200-250 g). Rats were allocated to daily training or remained sedentary for 3 days (N = 23) or 13 weeks (N = 23). After training, the carotid artery was catheterized for AP measurements. Locomotor (tibialis anterior and gracilis) and non-locomotor skeletal muscles (temporalis) were harvested and prepared for histologic and protein expression analyses. Training increased treadmill performance by all groups (SHR = 28 percent, WKY = 64 percent, 3 days) and (SHR = 141 percent, WKY = 122 percent, 13 weeks). SHR had higher values of AP than WKY (174 ± 4 vs 111 ± 2 mmHg) that were not altered by training. Three days of running increased VEGF expression (SHR = 28 percent, WKY = 36 percent) simultaneously with an increase in capillary-to-fiber ratio in gracilis muscle (SHR = 19 percent, WKY = 15 percent). In contrast, 13 weeks of training increased gracilis capillary-to-fiber ratio (SHR = 18 percent, WKY = 19 percent), without simultaneous changes in VEGF expression. Training did not change VEGF expression and capillarity of temporalis muscle. We conclude that training stimulates time- and tissue-dependent VEGF protein expression, independent of pressure levels. VEGF triggers angiogenesis in locomotor skeletal muscle shortly after the exercise starts, but is not involved in the maintenance of capillarity after long-term exercise in female rats.

Comparaçäo entre a prescriçäo de intensidade de treinamento físico baseada na avaliaçäo ergométrica convencional e na ergoespirométrica / Comparison between exercises intensity prescription based on a standard exercise test and cardiopulmonary exercise test

OBJETIVO - Comparar os limites inferiores (L.inf.) e superior (L.sup.) da pescriçäo de treinamento físico aeróbico determinada pelo teste ergométrico convencional (60-70 por cento do VO2máx estimulado ou 70-85 por cento da FCmáx atingida), com a prescriçäo obtida pelo teste ergoespirométrico [limiar anaeróbico (LA) e ponto de compensaçäo respiratória (PCR)]. MÉTODOS - Realizaram teste ergoespirométrico progressivo até a exaustäo 47 homens (30ñ5 anos), divididos em subgrupos, de acordo com a velocidade da esteira durante o teste (4 ou 5mph) e a capacidade física medida [baixa (BCF) e moderada (MCF)]. RESULTADOS - Os L.inf. de prescriçäo indireta apresentaram valores de VO2 e FC significantemente maiores que os valores de Vo2 e FC no LA...Os L.sup. de prescriçäo indireta no grupo de 4mph e BCF apresentaram valores de VO2 significantemente maiores que os valores medidos no PCR ..., e valores de FC semelhantes aos medidos no PCR. CONCLUSÄO - Os L.inf. da prescriçäo indireta de treinamento físico superestimam o LA, enquanto os L.sup. parecem adequados somente para indivíduos ativos com MCF

Validation of transit-time flowmetry for chronic measurements of regional blood flow in resting and exercising rats

The objective of the present study was to validate the transit-time technique for long-term measurements of iliac and renal blood flow in rats. Flow measured with ultrasonic probes was confirmed ex vivo using excised arteries perfused at varying flow rates. An implanted 1-mm probe reproduced with accuracy different patterns of flow relative to pressure in freely moving rats and accurately quantitated the resting iliac flow value (on average 10.43 + 0.99 ml/min or 2.78 + 0.3 ml min(-1) 100 g body weight(-1)). The measurements were stable over an experimental period of one week but were affected by probe size (resting flows were underestimated by 57 per cent with a 2-mm probe when compared with a 1-mm probe) and by anesthesia (in the same rats, iliac flow was reduced by 50-60 per cent when compared to the conscious state). Instantaneous changes of iliac and renal flow during excercise and recovery were accurately measured by the transit-time technique. Iliac flow increased instantaneously at the beginning of mild exercise (from 12.03 + 1.06 to 22.55 + 3.89 ml/min at 15 s) and showed a smaller increase when exercise intensity increased further, reaching a plateau of 38.43 + 1.92 ml/min at the 4th min of moderate exercise intensity. In contrast, exercise-induced reduction of renal flow was smaller and slower, with 18 per cent and 25 per cent decreases at mild and moderate exercise intensities. Our data indicate that transit-time flowmetry is a reliable method for long-term and continuous measurementes of regional blood flow at rest and can be used to quantitate the dynamic flow changes that characterize exercise and recovery.