DNA-PLOIDY CHANGES IN RHINO MOUSE SKIN INDUCED BY ALL-TRANS-RETINOIC ACID AND RETINOL

Objective: In order to assess the proliferative changes induced by all -trans retinoic acid (RA) and retinol (ROL), we have carried out a stu dy of the DNA content of basal and suprabasal keratinocytes after epic utaneous application on the rhino mouse. Study Design: Skin sections w ere analyzed stereologically and cytophotometrically using the Feulgen technique. The diploid DNA value (2C) was obtained from hepatocyte nu clei of control animals. Whereas cells in phase G(0)-G(1) will show a 2C content, cells during phase S and in phase G(2)-M will show DNA val ues ranging from 2C to 4C and 4C, respectively. Results: Although epid ermal thickness (ET) increased significantly in all treated animals, s urface density only increased in animals treated with all-trans RA. Qu antification of DNA content of basal keratinocytes showed reduction of 2C and 2C-4C populations with a commensurate increase in proportions of cells with 4C and >4C in the animals treated with 0.025% all-trans RA and ROL. Suprabasal keratinocytes of mice treated with 0.025% all-t rans showed a decrease of the 2C population and an increased proportio n of cells with 4C. Whereas 0.025% all-trans RA induced an increase of both basal and suprabasal DNA indices, ROL enhanced only the basal DN A index significantly. Conclusion: Animals treated with 0.025% ROL sho wed a significant increase in the basal proliferative index (PI) while the suprabasal PI remained constant; treatment with 0.025% all-trans RA produced a significant increase of both basal and suprabasal PIs an d parakeratotic hyperkeratosis probably due to incomplete differentiat ion.