To elucidate the mechanisms underlying the development of HgCl2-induced acute renal failure (ARF), we examined the expression of endothelin (ET)-1, endothelial (e) nitric oxide synthase (NOS) and inducible (i) NOS, and a role of angiotensin II (ANG II) and tumor necrosis factor (TNF) in glomeruli and cortices from rats at 20 h after exposure of HgCl2. Prepro-ET-1 and iNOS mRNA were significantly increased in glomeruli and cortices from rats with HgCl2-induced ARF. However, eNOS mRNA was markedly decreased in glomeruli of rats with HgCl2-induced ARF. Blockade of the action of endogenous ANG II with TCV-116, an ANG II receptor type 1 antagonist, or prior administration of TNF antibody (Ab) neutralizing TNF bioactivity or aminoguanidine, an iNOS inhibitor, substantially suppressed the increase in the expression of prepro-ET-1 or iNOS mRNA seen in rats with HgCl2-induced ARF. Both TCV-116 and TNF Ab had no effects on the expression of eNOS mRNA. The abundance of ET-1, iNOS, and eNOS proteins was paralleled by the magnitude of each mRNA expression. Additionally, the aggravation of blood urea nitrogen and serum Cr observed in rats with HgCl2-induced ARF were significantly ameliorated together with the alleviation of proximal tubule epithelial cell injury when the expression of prepro-ET-1 or iNOS mRNA was blunted by prior administration of TCV-116 or prior injection of TNF Ab or aminoguanidine. These observations indicate that ANG II, ET-1, and NO may play an important role in the progression of HgCl2-induced ARF through the acceleration of proximal tubule epithelial cell injury and the deterioration of glomerular hemodynamics. In HgCl2-induced ARF, the gene expression of ET-1 or iNOS is at least in part up-regulated at the transcription level by endogenous ANG II or TNF.