Doxorubicin induces male germ cell apoptosis in rats

To clarify whether apoptosis is involved in doxorubicin (DXR)-induced testi cular toxicity and to identify the target germ cell type, adult Sprague-Daw ley rats were treated with a single intravenous dose of DXR (8 or 12 mg/kg) and euthanized at 3, 6, 12, 24, and 48 h subsequently. Histologically, ger m cell degeneration was first found 6h after dosing in meiotically dividing spermatocytes and early round spermatids of seminiferous tubules at stage I, and subsequently observed in spermatogonia at stages I-VI showing ultras tructural characteristics of apoptosis. Coincident with the appearance of m orphological changes, degenerating germ cells were shown to be undergoing a poptosis as revealed by in situ terminal deoxynucleotidyl transferase-media ted dUTP nick end labeling (TUNEL). The frequency of TUNEL-labeled germ cel ls increased in a stage- and cell type-specific manner, the peak of frequen cy gradually progressing from stage I of seminiferous tubules to later stag es with time after dosing, suggesting that the damaged germ cells, especial ly spermatogonia, gradually underwent the processes leading to apoptosis. D NA laddering on gel electrophoresis was apparent 24 and 48 h after dosing. The results demonstrate that apoptosis plays an important role in the induc tion of testicular toxicity caused by DXR with meiotically dividing spermat ocytes and type A and intermediate spermatogonia as highly vulnerable targe t cells.