Inoue Y, Shibasaki M, Hirata K, Araki T
Laboratory for Human Performance Research, Osaka International University for Women, Moriguchi, Japan.
Eur J Appl Physiol Occup Physiol. 1998 Dec;79(1):17-23. doi: 10.1007/s004210050467.
To examine the mechanisms and regional differences in the age-related decrement of skin blood flow, 11 young (age 20-25 years) and 10 older (age 64-76 years) men were exposed to a mild heat stress by immersing their feet and lower legs in water at 42 degrees C for 60 min, while they were sitting in near thermoneutral conditions [25 degrees C and 45% relative humidity (rh)]. During the equilibrium period (25 degrees C and 45% rh) before the heat test, no group differences were observed in rectal (Tre) and mean skin (Tsk) temperatures or mean arterial pressure (MAP). During passive heating, Tsk was significantly lower in the older men 20 min after commencing exposure (P<0.001), although there were similar increases in Tre in both groups. Exposure time and age did not affect MAP. The local sweating rate (m(sw)) and the percentage change in skin blood flow by laser Doppler flowmetry (%LDF) relative to baseline values on the chest, back, forearm and thigh were significantly lower in the older men (P<0.001), especially on the thigh. After starting the heat exposure, three temporal phases were observed in the relationship between %LDF and m(sw) at most sites in each subject. In phase A, %LDF increased but with no increase in m(sw). In phase B, m(sw) increased but with no secondary increase in %LDF. Finally, in phase C, there were proportional increases in %LDF and m(sw). The increase in %LDF in phase A was significantly lower on the forearm and thigh (P<0.05) for the older men, but not on the chest and back. In phase C, the slopes of the regression lines between %LDF and m(sw) were lower for the older men on the back (P<0.03), forearm (P = 0.08) and thigh (P<0.03), but not on the chest. These results would suggest that the age-related decrement in skin blood flow in response to passive heating may be due in part to a smaller release of vasoconstrictor tone and to less active vasodilatation once sweating begins. Regional differences exist in the impaired vasoconstriction and active vasodilatation systems.
为研究皮肤血流随年龄增长而减少的机制及区域差异，11名年轻男性（年龄20 - 25岁）和10名老年男性（年龄64 - 76岁）在近乎中性温度条件下（25℃，相对湿度45%）坐着时，将双脚及小腿浸入42℃水中60分钟，使其暴露于轻度热应激环境。在热测试前的平衡期（25℃，相对湿度45%），两组在直肠温度（Tre）、平均皮肤温度（Tsk）或平均动脉压（MAP）方面未观察到差异。在被动加热过程中，开始暴露20分钟后老年男性的Tsk显著更低（P<0.001），尽管两组Tre的升高幅度相似。暴露时间和年龄对MAP无影响。老年男性胸部、背部、前臂和大腿的局部出汗率（m(sw)）以及激光多普勒血流仪测量的皮肤血流相对于基线值的百分比变化（%LDF）显著更低（P<0.001），尤其是大腿部位。热暴露开始后，每个受试者大多数部位的%LDF与m(sw)之间的关系观察到三个时间阶段。在A阶段，%LDF升高但m(sw)未升高。在B阶段，m(sw)升高但%LDF未二次升高。最后，在C阶段，%LDF和m(sw)成比例增加。老年男性在前臂和大腿A阶段%LDF的升高显著更低（P<0.05），但胸部和背部无此现象。在C阶段，老年男性背部（P<0.03）、前臂（P = 0.08）和大腿（P<0.03）的%LDF与m(sw)之间回归线的斜率更低，但胸部无此现象。这些结果表明，被动加热时皮肤血流随年龄增长而减少可能部分归因于血管收缩张力释放较小以及出汗开始后血管舒张活性较低。血管收缩和主动血管舒张系统受损存在区域差异。
