Afferent arteriolar dilation to 11,12-EET analogs involves PP2A activity and Ca2+-Activated K+ channels

The epoxygenase metabolite, 11,12-epoxyeicosatrictioic acid (11,12-EET), has renal vascular actions. 11,12-EET analogs have been developed to determine the structure activity relationship for 11,12-EET and as a tool to investigate signaling mechanisms responsible for afferent arteriolar dilation. We hypothesized that 11, 12-EET mediated afferent arteriolar dilation involves increased phosphoprotein phosphatase 2A (PP2A) and large-conductance calcium activated K+ (K-Ca) channels. We evaluated the chemically and/or metabolically stable 11,12-EET analogs: 11,12-EET-N-methylsulfonimide (11,12-EET-SI), 11-nonyloxy-undee-8(Z)-enoic acid (11,12-ether-EET-8-ZE), and 11,12-trans-oxidoeicosa-8(Z)-eotioic acid (11,12-tetra-EET-8-ZE). Afferent arteriolar responses were assessed. Activation of K-Ca channels by 11,12-EET analogs were established by single cell channel recordings in renal myocytes. Assessment of renal vascular responses revealed that 1 1,12-EET analogs increased afferent arteriolar diameter. Vasodilator responses to 11,12-EET analogs were abolished by K+ channel or PP2A inhibition. 11,12-EET analogs activated renal myocyte large-conductance K-Ca channels. 11.,12-EET analogs increased cAMP by 2-fold and PP2A activity increased 3-8 fold in renal myocytes. PP2A inhibition did not significantly affect the 11,12-EET analog mediated increase in cAMP and PP2A increased renal myocyte K-Ca channel activity to a much greater extent than PKA. These data support the concept that 11,12-EET utilizes PP2A dependent pathways to activate large-conductance K-Ca channels and dilate the afferent arteriole.