To study the time course of lipopolysaccharide-induced production of tumor necrosis factor-alpha (TNF-alpha) in the kidney, we utilized a highly sensitive non-radioisotopic in situ hybridization with 1-nm gold-conjugated anti-digoxigenin for localization of TNF-alpha mRNA expression after lipopolysaccharide administration. TNF-alpha mRNA expression localized by in situ hybridization showed a peak increment in proximal tubular epithelial cells and glomeruli at 2 hours and returned to almost normal levels at 6 hours. The intensity of the signal was much stronger in proximal tubules than in glomeruli. These findings were confirmed by the demonstration of similar kinetics in the increase of TNF-alpha message, measured by using amplification of the third and fourth exons of TNF-alpha gene by reverse transcription-polymerase chain reaction of microdissected proximal tubular segments and isolated glomeruli. Reverse transcription-polymerase chain reaction of cultured rat mesangial and glomerular epithelial cells demonstrated that mesangial cells, not glomerular epithelial cells, were responsible for the observed glomerular signals.