EXPRESSION OF KERATINS K6 AND K16 IN REGENERATING MOUSE EPIDERMIS IS LESS RESTRICTED BY CELL REPLICATION THAN THE EXPRESSION OF K1 AND K10

Biosynthesis of the hyperproliferation-associated keratins K6 and K16 was studied in mouse epidermis following a single topical application of the tumour promoter 12-O-tetradecanoylphorbol-13-acetate (TPA). An epidermal cell cohort was followed by pulse-labelling with the thymidi ne analogue 5-bromodeoxyuridine (BrdUrd). Mice were injected intraperi toneally with BrdUrd Ih before a single topical application of TPA. TP A induced regenerative epidermal hyperplasia with hyperproliferation a nd shortened suprabasal transit time. The BrdUrd-labelled cell cohort was followed for 96 h after TPA-treatment by two-colour immunofluoresc ence staining with antibodies to BrdUrd, keratin K6 and K16. In contro l animals, K6 and K16 were found only in the hair follicles. K6 expres sion was immediately induced in all epidermal cell layers of TPA-treat ed epidermis, including actively replicating cells and it was expresse d during the whole observation period. K16 was only present in postmit otic cells and was transiently expressed 8-72 h after TPA treatment. O ur results suggest that the expression of K6 and K16 is less restricte d by cellular replication than the normally occurring K1 and K10 kerat ins.