INTERSTITIAL CELL-PROLIFERATION IN THE TESTIS OF THE ETHYLENE DIMETHANE SULFONATE-TREATED RAT

This study was conducted to examine interstitial cell proliferation in the testis of the ethylene dimethane sulfonate (EDS)-treated rat. Initial autoradiographic studies demonstrated a peak of [H-3]thymidine incorporation by interstitial cells at 2 and 4 days post-EDS treatment. Subsequent studies were designed using in vivo pulse labeling regimens in an attempt to identify interstitial cell proliferation associated with Leydig cell regeneration. Rats were injected with [H-3]thymidine at days 2 and 4 post-EDS and were killed 6 hours later or at 30 days post-EDS. Although cells labeled at 2 and 4 days post-EDS appeared to undergo subsequent division, the Leydig cells visible at 30 and post-EDS were not labeled. In a second study, rats were injected with [H-3]thymidine at days 10 and 20 post-EDS and were killed either 6 hours later or at 24 days post-EDS. In the 10-day post-EDS group, interstitial cells were labeled at both the 6-hour and 24-day time points; however, Leydig cells present at 24 days were not labeled. In contrast, the testes of rats that killed at 20 days post-EDS (6 hours labeling period) contained Leydig cells that displayed grains over the nucleus, thus suggesting that Leydig cell proliferation had occurred. In addition, a high number of the Leydig cells observed at 24 days post-EDS were labeled, suggesting that they arose from divisions occurring during the 20- to 24-day post-EDS period. These studies demonstrate that interstitial cell proliferation occurs in several stages following EDS treatment. The initial peak of [H-3]thymidine incorporation, which occurs immediately after EDS treatment, was not shown to be directly related to Leydig cell development. A second, but smaller, peak of proliferation that occurs between 20 and 24 days post-EDS is directly related to Leydig cell development.