Steady-state mRNA expression and protein production of macrophage colony stimulating factor were measured in visually confluent monolayers of unstimulated cultured human retinal pigment epithelial cells and after cells were stimulated with recombinant cytokines. Using reverse transcription polymerase chain reaction, macrophage colony stimulating factor mRNA expression was detected in unstimulated cells obtained from each of four separate donors. In these cells, mRNA expression was accompanied by secretion of macrophage colony stimulating factor protein into cell-conditioned medium; 48 hr after cells were switched to fresh medium, the mean (+/- S.D.) quantity of macrophage colony stimulating factor, measured by enzyme-linked immunoassay, was 5.1 +/- 2.3 ng 10(-6) cells. There was a dose- and time-dependent induction of macrophage colony stimulating factor mRNA after cells were exposed to recombinant human interleukin-1 and tumor necrosis factor alpha. Maximal mRNA induction was observed in cells exposed for 4 hr to interleukin-1 beta (5 U ml-1) or for 4-8 hr to tumor necrosis factor alpha; under these conditions, macrophage colony stimulating factor mRNA was induced up to 23- and 46-fold after exposure to interleukin-1 beta and tumor necrosis factor alpha, respectively. Similarly, macrophage colony stimulating factor protein production was enhanced after cells were exposed to recombinant cytokines. Protein secretion increased 1.3-2.5-fold (P less than 0.001) after exposure to interleukin-1 beta (5 U ml-1), and 1.2-1.6-fold after exposure to tumor necrosis factor alpha (P less than 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)