Growth parameters of the hairless mouse epidermis after bleomycin treatment: possible interaction with epidermal chalones.

Hairless mice were given two injections of 2 mg bleomycin i.p. on two successive days. By a stathmokinetic method, micro-flow fluorometry and autoradiography, many kinetic parameters were measured. Bleomycin affected cell proliferation in epidermis by depressing the number of cells in and the passage of cells through the different cell cycle phases, i.e. S, G2 and M in a biphasic manner. The time between the two minima corresponded to the mean generation time of the basal cells. Skin extracts produced from animals at different time intervals after the bleomycin injection show that bleomycin interferred only slightly with the G1-chalone, but had a more pronounced effect on the content of G2 of the skin, increasing and reducing the chalone effect in a biphasic manner. The study gives some support to the theory that the particularly good effect of bleomycin in squamous cell epithelium may be due to an interference of bleomycin with keratinization and chalone production. The protein synthesis showed only a minimal depression where the kinetic parameters were heavily depressed.