EFFECT OF MELATONIN ON NORMAL AND SCLERODERMIC SKIN FIBROBLAST PROLIFERATION

Objective. We studied the effect of melatonin (MLT) (N-acetyl5-methoxy tryptamine) on the growth rate of normal skin fibroblasts and of fibro blasts from involved and apparently uninvolved skin of patients affect ed by systemic sclerosis (SSc). Methods. The growth rate was evaluated on the basis of growth curves and a H-3-thymidine incorporation assay . Results. Our results demonstrate that a dose of 200 mu g/ml of MLT i nhibits (> 80%) both control and SSc fibroblasts. Inhibition was dose- dependent and was greater than 70% for MLT concentrations of 100 mu g/ ml, 200 mu g/ml and 400 mu g/ml. H-3-thymidine incorporation was corre lated with the effect on the growth curves (81% at 200 mu g/ml of MLT) . In contrast, at a low dosage of 6 mu g/ml, MLT exerted a stimulatory effect on cell proliferation in all the cell lines analyzed. Cell via bility was not affected by MLT at any of the concentrations tested. A recovery study indicated that replacement of MLT-containing medium wit h MLT-free medium resulted in a re-establishment of cell growth. Concl usion. These results suggest that MLT, at higher dosages, is a potent inhibitor of the proliferation of fibroblasts derived from the skirt o f healthy and SSc patients.