Greenleaf J E
Fed Proc. 1982 Jul;41(9):2509-14.
Mechanisms of drinking have been studied extensively in laboratory mammals, but comparatively little information is available on human consumption of fluids. The assumption that osmotic disequilibrium between extra- and intracellular fluid can be rectified within seconds may not be true for plasma and red blood cell (RBC) fluid in humans inasmuch as stress-induced hyperosmotemia to +13 mosmol/kg does not cause a significant change in mean RBC corpuscular volume. Unlike some mammals, humans have a delay in rehydration (involuntary dehydration) after fluid loss. Two factors unique to humans that probably contribute to involuntary dehydration are 1) upright posture and 2) extracellular fluid and electrolyte loss by sweating from exercise and heat exposure. If drinking is influenced by upright postural changes, it may be related to increased plasma renin activity (PRA) but not to increases in plasma osmolality or arginine vasopressin concentration. Under combined stresses of heat, exercise, and prior dehydration, exercise is the greatest inhibiting factor and heat exposure has the least inhibitory effect on voluntary water intake. The rate of drinking during exercise in heat has a high correlation with sweat rate but is essentially unrelated to the well-established dipsogenic factors of plasma volume, osmolality, and PRA. However, it is likely that some or all of these dipsogenic factors act to initiate drinking in humans.
人们已在实验哺乳动物中广泛研究了饮水机制，但关于人类液体摄入的信息相对较少。细胞外液和细胞内液之间的渗透失衡可在数秒内得到纠正，这一假设对人类血浆和红细胞（RBC）液体而言可能并不成立，因为应激诱导的高渗血症至 +13 毫摩尔每千克并不会导致平均红细胞体积发生显著变化。与一些哺乳动物不同，人类在液体流失后补水（非自愿性脱水）存在延迟。可能导致非自愿性脱水的两个独特的人类因素是：1）直立姿势；2）运动和热暴露引起的出汗导致细胞外液和电解质流失。如果饮水受直立姿势变化影响，可能与血浆肾素活性（PRA）增加有关，而与血浆渗透压或精氨酸加压素浓度增加无关。在热、运动和先前脱水的综合应激下，运动是最大的抑制因素，热暴露对自愿水摄入的抑制作用最小。在热环境中运动时的饮水速率与出汗速率高度相关，但与已确定的血浆容量、渗透压和 PRA 等致渴因素基本无关。然而，这些致渴因素中的一些或全部可能在人类中引发饮水行为。
