Recent studies suggest that tissue specific fibroblasts respond to inflammatory stimuli leading to the onset of inflammatory disorders. In the present study, we investigated cell kinetics, collagen synthesis, and nitric oxide (NO) level in cultured human small intestinal lamina propria fibroblasts (HSILPF, n = 45) in response to LPS of enteropathogenic E. coli. LPS treatment enhanced the 3[H] TdR uptake, increased the percentage of 'S' phase cells as early as 4 hrs, and decreased the population doubling time of HSILPF in a dose and time dependent manner. Collagen synthesis in HSILPF was also elevated by LPS. The LPS induced cell proliferation and collagen synthesis were inhibited by polymyxin B (10 micrograms/ml). LPS was found to suppress the NO production in these cells, whereas combination of LPS (10 micrograms/ml) and IFN gamma (100 U/ml) enhanced NO output and concurrently decreased the cell proliferation and collagen production in HSILPF. Inhibitors of NO, L-NG-monomethyl L-arginine, and aminoguanidine partially restored cell proliferation and collagen synthesis in cells exposed to LPS and IFN gamma. These findings suggest that LPS induces increased cell proliferation and collagen synthesis in HSILPF and these could be related to the suppression of NO production.