P-glycoprotein and cell volume-activated chloride channels.

The multidrug resistance P-glycoprotein (P-gp) is an active drug transporter which can expel hydrophobic compounds from cells. Expression of P-gp has many effects on cells and tissues and the physiological function, or functions, of P-gp are still unclear. Recently, expression of P-gp has been associated with altered activity of chloride channels which play a role in regulating cell volume of response to osmotic shock or nutrient uptake. The nature and physiological role of this association has been a subject of some debate. In this article, mechanisms by which P-gp might influence cell volume-activated chloride currents is discussed, and the potential physiological role of this regulation considered.