Previous work showed that uninephrectomized (NPX) rats are more susceptible to the nephropathy induced by some doses of HgCl2 than sham-operated (SHAM) rats. The aim of the present study was to investigate the cytotoxic effects of HgCl2 in proximal tubular (PT) cells isolated from the kidney(s) of both NPX and SHAM rats. The study was designed to test if isolated PT cells that have undergone compensatory hypertrophy in vivo are more sensitive to the cytotoxic effects of HgCl2 in vitro than PT cells isolated from the kidneys of control animals. PT cells were purified from suspensions of renal cortical cells by Percoll density gradient centrifugation. The cellular content of protein (mg/10(6) cells) was 68% higher and the cellular specific activity (mU/10(6) cells) of lactate dehydrogenase was 56% higher in PT cells isolated from NPX rats than in PT cells isolated from SHAM rats. The cytotoxicity of HgCl2, as assessed by inhibition of lactate dehydrogenase activity, exhibited a steep concentration dependence. In the presence of bovine serum albumin, PT cells from both NPX and SHAM rats displayed no signs of cellular injury at concentrations of HgCl2 less than or equal to 0.1 mM. At concentrations of HgCl2 greater than or equal to 0.25 mM, cellular necrosis occurred rapidly in all PT cells. In the absence of bovine serum albumin, cellular injury and death occurred at concentrations of HgCl2 as low as 0.01 mM. PT cells from NPX rats exhibited signs of cellular injury at lower concentrations of HgCl2 than PT cells from SHAM rats when BSA was absent from the extracellular medium. Preincubation of PT cells from both NPX and SHAM rats with glutathione provided the cells with concentration-dependent protection from the cytotoxic effects of HgCl2. Preincubation of PT cells from both NPX and SHAM rats with the chelating agent 2,3-dimercapto-1-propane sulfonate provided cells with complete protection from the cytotoxic effects of HgCl2 when the concentration of 2,3-dimercapto-1-propane sulfonate was slightly below or higher than the concentration of HgCl2. Results of this study demonstrate the usefulness of freshly isolated PT cells from NPX rats as an in vitro model system to investigate biochemical mechanisms by which compensatory renal growth alters susceptibility to chemical-induced nephrotoxicity.