Abstract

Aquaporin-2 (AQP2) is a vasopressin-regulated water channel responsible for regulating water reabsorption through the apical plasma membrane of the principal cells of renal collecting ducts. It has been found that dysregulation and dysfunction of AQP2 cause many disorders related to water balance in people and animals, including polyuria and dilutional hyponatremia. Classically, AQP2 mRNA and protein expression and its membrane translocation are regulated by systemic vasopressin involving short-term regulation of AQP2 trafficking to and from the apical plasma membrane and long-term regulation of the total amount of the AQP2 protein in the cell. Recently, increasing evidence has demonstrated that collecting duct AQP2 expression and membrane translocation are also under the control of many other local factors, especially nuclear receptors. Here, we briefly review the progress of studies in this area and discuss the role of nuclear receptors in the regulation of water reabsorption via affecting AQP2 expression and function.

Introduction

Water is a basic necessity of life and is the main component of extracellular fluid. Normally, the body’s water content (50%–۶۰% of body weight) and osmotic pressure of extracellular fluid (280–۲۹۵ mOsm/kg) play a critical role in maintaining homeostasis, which is achieved through the regulation of water intake and loss. Daily water intake from drinking and food and endogenous production of water via the body’s metabolism provide approximate 1.5–۳٫۰ L. Accordingly, water is excreted from the kidneys, lungs, skin and gastrointestinal tract to maintain water homeostasis of whole body. It is wildly accepted that urine produced from the kidney is the main way to mediate water output from the body.