H2O2 and Src-dependent transactivation of the EGF receptor mediates the stimulatory effect of leptin on renal ERK and Na+, K+-ATPase

We examined the mechanism through which leptin increases Na⁺, K⁺-ATPase activity in the rat kidney. Leptin was infused under anaesthesia into the abdominal aorta proximally to the renal arteries and then Na⁺, K⁺-ATPase activity was measured in the renal cortex and medulla. Leptin (1 μg/kg min) increased Na⁺, K⁺-ATPase activity after 3 h of infusion, which was accompanied by the increase in urinary H₂O₂ excretion and phosphorylation level of extracellular signal regulated kinase (ERK). The effect of leptin on ERK and Na⁺, K⁺-ATPase was abolished by catalase, specific inhibitors of epidermal growth factor (EGF) receptor, AG1478 and PD158780, as well as by ERK inhibitor, PD98059, and was mimicked by both exogenous H₂O₂ and EGF. The effect of leptin was also prevented by the inhibitor of Src tyrosine kinase, PP2. Leptin and H₂O₂ increased Src phosphorylation at Tyr⁴¹⁸. We conclude that leptin-induced stimulation of renal Na⁺, K⁺-ATPase involves H₂O₂ generation, Src kinase, transactivation of the EGF receptor, and stimulation of ERK.