Comparative analysis of MO survival, secreted M-CSF protein, and M-CSF mRNA level after RA treatment. MO were cultured for 2 days and 4 days, respectively, on teflon foils with or without 10⁻⁷ mol/L RA. Cells were harvested, counted, and lysed with guanidine thiocyanate solution. Northern analysis was performed as described in the Materials and Methods. Densitometric analysis of the signals was performed. M-CSF content of the corresponding supernatants was determined by ELISA. All values are given as the mean percentage of inhibition by RA compared with the serum control (results are significantly different: for survival, day 2 [P < .02] and day 4 [P < .0001]; for M-CSF protein, day 2 [P < .03] and day 4 [P < .009]; for M-CSF mRNA, day 4 [P < .05] by two-tailed t-test for paired data). Results are not significantly different for day 2 mRNA data.