The role of aquaporins in the regulation of body fluids homeostasis

Abstract

The rapid transfer of the water across the cells occurs via specialized channels called aquaporins (AQPs). The structure of AQPs comprises of homotetramers with each of the four units functioning as an independent channel. The distribution of total body water is into intracellular (40% of total body weight) and extracellular compartments (20% of total body weight). While there is some degree of physical separation of the compartments, water freely moved between them with the intent of achieving homeostasis. The typical role of AQP is to act as an effector in the regulation of water at cellular, tissue and organ levels, although recent evidence suggested it can also act as a sensor-effector system. The regulatory roles include cell volume regulation (CVR), which comprises of regulatory volume decrease and regulatory volume increase. The AQPs are also involved in the total body water homeostasis via short- and long-term regulatory mechanisms. The short-term water regulation takes place within minutes, and it typified by insertion of AQP2 into the apical cell membrane of collecting duct following activation of V2 receptor by vasopressin. The long-term regulation by the AQPs involves increased expression of AQPs. Hence, this narrative reviewed the importance of AQPs in the ability to facilitate highly efficient, yet strictly selective permeation of small molecules including water, solutes, and ions, transport across the plasma membrane as it relates to body fluid homeostasis.