Aquaporin in mammalian species: A review

The discovery of water specific channels answered the longstanding biophysical and biochemical question relating water transport across different biological membranes and at the molecular level provided a full insight into the fundamental physiology of water balance and the pathophysiology associated with its dysfunction. Data revealing the presence of Aquaporin (AQP) in sperm is scanty, but most of its isoforms except AQP6 and AQP12 are found in different organs including testes, efferent ducts and epididymis. Presence of mainly AQP1 and AQP9 in the efferent duct plays a crucial role in the reabsorption/secretion dynamics of the luminal fluid during maturation process and transport of the sperm. Localization of other isoforms namely AQP3, AQP7, AQP8 and AQP11 has been confirmed in the sperm where it is found to be involved in volume regulation, which is required for the differentiation of spermatids into spermatozoa during spermiogenesis process as well as facilitates sperm transit along environments of different osmolarity (male and female reproductive tract). In the present review we cover the mechanisms underlying regulation of this protein and the associated pathophysiology which will throw a light for new research ventures regarding the manipulation of this protein for sequential management of disorders associated with water balance.