Radioautographic Study of Epidermal Cell Proliferation and Migration in Normal and Neoplastic Tissues of Rabbits

Summary

The tritiated thymidine (³H-TDR) radioautography technique was used to examine the kinetics of cellular proliferation and migration in skin papillomas of rabbits induced by the virus of Shope (SPV). The mean cell cycle time in the domestic rabbit Shope papilloma was 21.2 hours and the mean durations of S, G₂, M, and G₁ phases were 5.3, 4.8, 0.3, and 10.8 hours, respectively. The pattern of cell migration in the cottontail Shope papilloma resembled that in the domestic rabbit Shope papilloma. Maximal labeling occurred in the granular layer between 32 and 80 hours in the former and between 60 and 84 hours in the latter tumor. The label could not be detected in the Shope papillomas 1 week after ³H-TDR injection, but it persisted in the dorsal epidermis up to day 14. A comparison of the labeling indices was made between 3 tumors induced by SPV, 3 other tumors induced by the chemical carcinogen 7,12-dimethylbenz[a]anthracene, and the normal epidermis of rabbits. The indices were 4–6 times greater in the viral and chemical tumors than in the normal counterpart, the dorsal epidermis. Similarly at 3 hours after ³H-TDR injection, the tumors showed 4–10 times as many labeled cells in the basal layer as in the dorsal epidermis.