PGE2 inhibits ROMK channels in the CCD through activation of MAPK pathway

Abstract

We have used the patch clamp technique and Western blot analysis to explore the effect of PGE2 on ROMK-like small conductance K (SK) channels in the CCD. Application of 10 uM PGE2 inhibited SK channels in the CCD. Moreover, inhibition of P38 and ERK MAPK not only increased SK channel activity but also abolished the effect of PGE2 on SK in the CCD. To determine whether PGE2 stimulates the phosphorylation of P38 and ERK, we treated mouse CCD cells (M-1) with PGE2. Application of PGE2 significantly stimulated the phosphorylation of P38 and ERK within 5 min. The dose response curve of PGE2 effect shows that 1, 5 and 10 uM PGE2 increased the phosphorylation of ERK and P38 by 25, 50 and 80%, respectively. The stimulatory effect of PGE2 on MAPK phosphorylation was not affected by indomethacin but abolished by inhibition of PKC. This suggests that the effect of PGE2 on MAPK phosphorylation requires PKC. Also, we examined the COX2 expression in the rat kidney. The expression of COX2 and PGE2 concentration in renal cortex and outer medulla were significantly higher in rats fed on K-depleted diet (KD) than that on a normal K. We conclude that PGE2 inhibits SK channels in the CCD through MAPK pathways and that high concentrations of PGE2 induced by K restriction may be partially responsible for increasing MAPK activity during K restriction.