Because ecto-5'-nucleotidase activity of rat glomerular mesangial cells has been shown to increase upon interaction with macrophages in vitro, it was examined whether interleukin-1 beta (IL-1 beta) and tumour necrosis factor-alpha (TNF-alpha), two macrophage-released cytokines, were responsible for this effect. IL-1 beta and TNF-alpha stimulated mesangial cell 5'-nucleotidase activity in a dose-dependent manner after treatment for 24 hr. Maximum increases reached 4.5 times and 1.7 times basal values for IL-1 beta (20 U/ml) and TNF-alpha (25 ng/ml), respectively. The effects of both cytokines were additive. Stimulation of 5'-nucleotidase by IL-1 beta and TNF-alpha was specific since the activity of other ectoenzymes, such as Mg2(+)-ATPase, was unchanged. Cycloheximide, a blocker of protein synthesis, suppressed the cytokine-dependent increase of 5'-nucleotidase activity. Cyclo-oxygenase inhibitors such as indomethacin and ibuprofen inhibited approximately 50% of the effects of both cytokines. Their inhibitory effect was abolished in the presence of prostaglandin E2 (PGE2). In addition, PGE2 itself produced a dose-related (0.1-10 microM) increase of 5'-nucleotidase activity with a maximum of 2.2 times basal value. Taken together, these results indicate that IL-1 beta, essentially, and TNF-alpha, to a lesser extent, regulate 5'-nucleotidase expression in the plasma membrane of cultured mesangial cells and that their effect depends in part on PGE2 synthesis. Therefore, macrophages, via their products of secretion acting on 5'-nucleotidase, could modulate adenosine production in the glomerular capillaries.