Prostaglandin E ₂ stimulates the epithelial sodium channel (ENaC) in cultured mouse cortical collecting duct cells in an autocrine manner

摘要

In murine cortical collecting duct cells, prostaglandin E _(2) (PGE _(2)) stimulates transepithelial sodium transport mediated by the epithelial sodium channel (ENaC). PGE _(2) is synthesized and secreted by the cells and acts on basolateral prostaglandin E receptor type 4 (EP _(4)). Prostaglandin E _(2) (PGE _(2)) is the most abundant prostanoid in the kidney, affecting a wide range of renal functions. Conflicting data have been reported regarding the effects of PGE _(2) on tubular water and ion transport. The amiloride-sensitive epithelial sodium channel (ENaC) is rate limiting for transepithelial sodium transport in the aldosterone-sensitive distal nephron. The aim of the present study was to explore a potential role of PGE _(2) in regulating ENaC in cortical collecting duct (CCD) cells. Short-circuit current (I _(SC)) measurements were performed using the murine mCCD _(cl1) cell line known to express characteristic properties of CCD principal cells and to be responsive to physiological concentrations of aldosterone and vasopressin. PGE _(2) stimulated amiloride-sensitive I _(SC) via basolateral prostaglandin E receptors type 4 (EP _(4)) with an EC _(50) of ～7.1 nM. The rapid stimulatory effect of PGE _(2) on I _(SC) resembled that of vasopressin. A maximum response was reached within minutes, coinciding with an increased abundance of β-ENaC at the apical plasma membrane and elevated cytosolic cAMP levels. The effects of PGE _(2) and vasopressin were nonadditive, indicating similar signaling cascades. Exposing mCCD _(cl1) cells to aldosterone caused a much slower (～2 h) increase of the amiloride-sensitive I _(SC). Interestingly, the rapid effect of PGE _(2) was preserved even after aldosterone stimulation. Furthermore, application of arachidonic acid also increased the amiloride-sensitive I _(SC) involving basolateral EP _(4) receptors. Exposure to arachidonic acid resulted in elevated PGE _(2) in the basolateral medium in a cyclooxygenase 1 (COX-1)–dependent manner. These data suggest that in the cortical collecting duct, locally produced and secreted PGE _(2) can stimulate ENaC-mediated transepithelial sodium transport.