Endothelin-1 stimulates cyclic GMP formation in porcine kidney epithelial cells via activation of the L-arginine-dependent soluble guanylate cyclase pathway

Abstract

Endothelin-1 (ET-1) elevated cyclic GMP levels in cultured porcine kidney epithelial cells (LLC-PK1) in a concentration-dependent manner with an EC50 value of about 5 x 10(-10) M. NG-methyl-L-arginine and NG-nitro-L-arginine inhibited cyclic GMP responses to 10(-8) M ET-1 with IC50 values of 1.2 x 10(-6) and 7.6 x 10(-8) M, respectively, and the inhibition was prevented with L-arginine. ET-1-induced cyclic GMP accumulation was enhanced with superoxide dismutase and diminished with oxyhemoglobin and methylene blue. Furthermore, the effect of ET-1 on the cyclic GMP levels was totally dependent on extracellular Ca2+. ET-3, but not big ET-1 and ET C-terminal hexapeptide16-21, elicited similar cyclic GMP responses as observed with ET-1 at the same concentration range. These data strongly suggest that, in LLC-PK1 cells, ET-1 stimulates formation of an endothelium-derived relaxing factor-like substance from L-arginine in a Ca(2+)-dependent fashion, which in turn activates soluble guanylate cyclase to elevate cellular cyclic GMP levels. The effects of ET on cyclic GMP accumulation in the kidney epithelial cells may be related to the natriuretic effects of ET in vivo.