Acute adverse effects of the indenopyridine CDB-4022 on the ultrastructure of sertoli cells, spermatocytes, and spermatids in rat testes: comparison to the known sertoli cell toxicant Di-n-pentylphthalate (DPP).

Acute effects of CDB-4022 on testicular ultrastructure were determined. Rats were treated orally with vehicle or a maximally effective single dose of CDB-4022 or Di-n-pentylphthalate (DPP). Preserved testes were processed for transmission electron microscopy. Sertoli and germ cells of vehicle-treated rats demonstrated normal morphological characteristics. Disruption of Sertoli cell ultrastructure was apparent in CDB-4022-treated rats by 3 hours. A decrease in the presence of nucleoli, an increase in the amount and diameter of swollen smooth endoplasmic reticulum, and decreases in cytoplasmic ground substance were observed. The severity of these degenerative effects increased at 6 and 12 hours: Vacuoles were apparent; increased cellular debris, swollen mitochondria, and phagocytic structures were observed; and membranes became more disorganized. Similar ultrastructural changes were observed in the Sertoli cells of DPP-treated rats. By 3 hours, spermatocytes and spermatids were adversely affected by CDB-4022 treatment with swelling of the nuclear envelope. The Step 8 spermatids were especially noteworthy; chromatin was more diffuse and rarefied, the nuclear envelopes were incomplete or broken, and the position of the spermatid nucleus within the cell and relative to Sertoli cell cytoplasm was unusual. Fusion of spermatids to form giant cells was observed by 12 hours. CDB-4022 acts acutely on Sertoli cells to induce marked cellular rarefaction and degeneration, but not necrosis. A rapid and direct effect of CDB-4022 on spermatocytes and spermatids was observed. The antispermatogenic activity of CDB-4022 appears to be a consequence of direct effects on Sertoli and germ cells.