Epithelial Na⁺ channels (ENaC) control sodium and fluid homeostasis and regulate blood pressure. In addition to being tightly regulated by well-known hormonal and homocellular factors, recent studies in A6 epithelial cells indicate that ENaC activity may be influenced by a membrane lipid [1,2], phosphatidylinositol 4,5-bisphosphate (PIP2). The detail mechanism by which PIP2 regulates ENaC activity is still not known. In this study we used whole cell patch-clamp techniques to investigate the physiological role of PIP2 in regulating transepithelial Na⁺ absorption. Amiloride-sensitive Na⁺ conductance was measured in duct cells prepared from mandibular glands of Quackenbush mice post mortem [3]. After holding the whole-cell configuration for 3 min, the whole-cell current was measured. The observed difference between the currents with and without 100 µM amiloride was used to calculate the amiloride-sensitive Na⁺ conductance. Under control conditions, the amiloride-sensitive chord conductance of the duct cells was 306.4 ± 33.4 pS (n = 19). Addition of an antibody directed against PIP2 (60 nM) to the pipette solution reduced the amiloride-sensitive conductance by 44.5% to 170.1 ± 12.5 pS (n = 8, P < 0.05) whereas heat-inactivated PIP2 antibody was without effect. Therefore, PIP2 activity may contribute to maintenance of ENaC function in duct cells. The effect of PIP2 on ENaC is believed to be mediated via ENaC β and γ N-termini [4]. Inclusion in the pipette solution of either β- or γ-ENaC N-terminal peptides containing the consensus PIP2 binding sites inhibited ENaC activity by more than 60%. Interestingly, inclusion of 25 μM PIP2 in the pipette solution prevented ENaC from being downregulated by high cytosolic Na⁺ concentration. The mechanism by which PIP2 inhibits Na⁺ feedback regulation of ENaC in the duct cell is currently under investigation.