Insulin, insulin-like growth factor (IGF1) and aldosterone increase sodium reabsorption in the distal nephron, thereby contributing to the control of extracellular fluid volume and blood pressure. Studies in amphibian cell monolayers (A6) have established that the increase in sodium transport induced by insulin, aldosterone as well as H₂O₂ involves the activation of phosphatidylinositol 3-kinase (PI 3-kinase), although with different time courses. Although A6 cell monolayers have yielded many fundamental results, these have to be reproduced in mammalian cells culture as differences obviously exist. For exemple, sodium transport across amphibian cell monolayers requires higher concentrations of hormones. The goal of the present study is to establish a mammalian model of distal nephron that can respond to physiological concentrations of hormones in order to study the stimulation of sodium transport by different agonists of PI 3-kinase. While the laboratory of Rossier has established that aldosterone (0.3 nM) and IGF1 (0.3 nM) increase sodium transport, we show here that H₂O₂ also increases sodium transport across mCCD cell monolayers. Each of these stimulations is PI-3kinase-dependent as preincubation of the monolayers with the PI 3-kinase inhibitor (LY294002) prevents any increase of sodium transport by the different agonists. Of interest, the fact that H₂O₂ also provokes an increase in PI 3-kinase activity leading to subsequent rise in sodium transport, may suggest its involvement as a critical mediator of hormonal-stimulated transport. Indeed, H₂O₂ produced within cells by a NADPH oxidase following hormone stimulation could activate PI 3-kinase.