Comparative effects of X irradiation on the testes of adult Sprague-Dawley and Wistar rats.

The response of the testes of two strains of adult rats (Sprague-Dawley and Wistar) to graded single doses and split doses of 230 kVp X rays has been investigated. A marked difference was noted between the strains in the response of the clonogenic spermatogonia to irradiation, as measured histologically by the repopulation index. Single-dose response curves derived for these cells in the Sprague-Dawley strain had a much larger shoulder (up to about 4-5 Gy) than for the Wistar (less than 2 Gy). Split-dose studies revealed that this difference may partly be explained by a greater repair capacity in the cells of the Sprague-Dawley strain. Changes in serum FSH concentrations mirrored the changes in clonogenic spermatogonial survival following split doses of radiation.