PHYSIOLOGY OF WATER BALANCE--RESEARCH AND EDUCATION PROJECT

溶质和水分平衡失调是世界各地几乎所有医学领域发病率和死亡率的一个重要原因。因此，对水和溶质稳态的生理和病理生理的工作知识对每个执业医生都是必不可少的。控制人体溶质和水分平衡的主要因素是众所周知的。其中一些，如调节肾脏水和溶质排泄的机制，已经在细胞水平和整个身体水平上进行了广泛的研究。然而，对于其他重要变量的调节，如摄入或外输出，我们所知甚少。关于调节系统的各个部分如何在正常活动期间或在经常研究和治疗患者的情况下相互作用以维持健康人体内水分和溶质平衡的可靠信息就更少了。在这方面尤其缺乏关于个人之间以及不同年龄、性别、族裔或种族群体之间正常差异的范围和原因的可靠数据。例如，很明显，健康的年轻白种人成年男女在口渴和抗利尿激素精氨酸抗利尿素分泌的渗透调节方面表现出非常大的、由基因决定的个体间差异(1)，但尚不清楚这些差异如何转化为总体水和溶质稳态的个体差异。关于成人正常尿量变化的最佳信息(2)表明，尿量变化范围为600至1600毫升/24小时，但这些值与性别、种族、环境条件或体型或溶质负荷的变化无关。此外，这个正常范围的有效性是非常可疑的，因为最近一项对12名CRC健康青年志愿者的研究（3,4）显示，其中25%的人的尿量在1800到3600毫升/24小时之间。显然，重要的是要确定这种差异是由于早期研究中的错误方法，住院治疗或我们自己的研究中的选择偏差，还是仅仅是由于过去50年饮食习惯的文化变化。类似的不确定性也适用于公布的尿溶质排泄、液体摄入和不敏感水分流失的正常值，这些正常值也必须因遗传和环境因素而因人而异。需要澄清这些问题，以便为区分个别患者的疾病与正常变异提供更合理的基础。

Disorders of solute and water balance are a significant cause of morbidity and mortality in virtually all areas of medicine in every part of the world. Thus, a working knowledge of the physiology and pathophysiology of water and solute homeostasis is essential for every practicing physician. The principal elements in the control of solute and water balance in humans are well known. Some of them, such as the mechanisms that regulate the renal excretion of water and solute, have been studied extensively at the level of the cell as well as the whole body. However, much less is known about the regulation of other important variables such as intake or extrarenal output. There is even less reliable information about the way the various parts of the regulatory system interact to maintain water and solute balance in healthy people during normal activities or under the conditions in which patients are often studied and treated. Particularly lacking in this regard are reliable data concerning the scope and causes of normal variation between individuals as well as between different age, gender, ethnic or racial groups. It is clear, for example, that healthy young caucasian adults of both sexes show very large, genetically determined inter-individual differences in the osmoregulation of both thirst and secretion of the antidiuretic hormone, arginine vasopressin (1) but it is not known how these differences translate into individual variation in overall water and solute homeostasis. The best available information on normal variation in urine volume in adults (2) indicates a range from 600 to 1600 ml/24 hours but does not relate these values to gender, race, environmental conditions or variations in body size or solute load. Moreover, the validity of this normal range is highly dubious because a recent study of 12 healthy young adult volunteers in the CRC (3,4)revealed that 25% of them had urine outputs between 1800 and 3600 ml/24hours. Clearly, it is important to determine if this discrepency is due to faulty methodology in the earlier study, to hospitalization or selection bias in our own study or simply to cultural changes in eating and drinking habits in the last 50 years. Similar uncertainties pertain to the published normal values for urinary solute excretion, fluid intake and insensible water loss which must also vary markedly from person to person depending on genetic and environmental factors. Clarification of these issues is needed to provide a more rational foundation for differentiating disease from normal variation in individual patients.