Spermatogonial cell renewal under continuous irradiation at 1.8 and 45 rads per day

The cell population kinetics and radiation response of continuously irradiated C57BL/6J mouse testes have been analysed. The changes in spermatogonial cell population sizes and cell kinetic parameters have provided information on the degree of radiosensitivity within the seminiferous epithelium at sublethal continuous irradiation doses and the manner in which the tissue responds. At 1.8 rad/d, spermatogonial cell renewal was maintained at near-normal levels through compensatory cell proliferation and recruitment from the Asub(s) stem cell pool. However, at 45 rad/d, depopulation of the testes took place through radiation depletion and maturation-differentiation of surviving elements. At this higher dose rate, the five type-A subpopulations were maintained at near-steady states of growth. The seminiferous epithelium displayed a remarkable capacity to recover. After two weeks of continuous irradiation at 45 rad/d, recovery commenced with proliferation from the Asub(s) spermatogonial stem cells, leading to full restoration of the seminiferous epithelium. (author)