MORPHOLOGIC AND METABOLIC CHANGES IN RAT OSTEOBLAST CULTURES DURING THE DARK REACTION WITH 8-METHOXYPSORALEN

The dark reaction of 8-methoxypsoralen (8-MOP) with cultured rat osteo blasts did not cause significant changes in cellular replication rates or in the synthesis of RNA and proteins. Microscopic examination, how ever, revealed that the dark reaction resulted in massive accumulation of perinuclear lipids and in the statistically significant enhancemen t of alkaline phosphatase activity. A sharp, and statistically signifi cant, upsurge of lipid synthesis in osteoblasts preceded microscopical ly detectable accumulation of lipids and occurred only during the init ial, but not during the subsequent stages of the dark reaction. These results suggest that in the course of the dark reaction the plasma mem brane of osteoblasts is a target of psoralen.