Modifications of doubling potential of cultured human diploid cells by ionizing radiation and hydrocortisone

Abstract

Cells possessing the ability to multiply into colonies have advanced successively to the next colony formation, which makes it possible to estimate the maximum doubling potential in the human diploid cell population. Attempts were made to modify the population doubling potential and the maximum doubling potential of human diploid cells with external agents. X-ray irradiation at high dose rates reduced the population doubling potential (Ban et al., 1980), while hydrocortisone had the advantage of extending the population life span, as has neen reported. The magnitude of extension acquired was equivalent to about a quarter of the non-treated population's life span. However, X-irradiation and hydrocortisone treatment failed to change the maximum doubling potential. This means that ionizing radiation might accelerate the progression of cells to non-cycling state, while hydrocortisone might decelerate it. Our results support the hypothesis that the growth and death of cultured human diploid cells might reflect cell differentiation in vitro (Bell et al., 1978).