The underlying primary damage to the seminiferous epithelium caused by 
chemotherapeutic regimens at childhood is largely unknown. The present 
investigation was designed to identify acute cytotoxic events in the testis 
caused by a single dose of doxorubicin. Male rats at 6, 16, and 24 days of age 
were injected with doxorubicin (3 mg/kg, i.p.) or vehicle (saline) alone and 24 
and 48 hours later, the germ cell types and apoptotic cells in the seminiferous 
epithelium were examined. As indicated by microscopy and terminal 
deoxyribonucleotidyl transferase-mediated dUTP nick end labeling staining, an 
8-fold increase in the number of apoptotic germ cells in the testes of 6-day-old 
rats was observed 48 hours after doxorubicin treatment. Spermatogonia migrating 
to the basement membrane were the primary cell type undergoing this induced 
apoptosis. A single dose of amifostine (200 mg/kg) administered i.p. 15 minutes 
before injection of doxorubicin provided no protection against this enhanced 
apoptosis. Under the same conditions, testicular levels of p53 and activated 
caspase 8 were elevated, whereas the level of murine double minute-2 was 
lowered. In contrast, doxorubicin treatment did not result in any significant 
change in the physiologic, stage-specific germ cell apoptosis occurring in the 
testes of 16- and 24-day-old rats. These observations suggest that the 
initiation phase of spermatogenesis is highly sensitive to doxorubicin-induced 
apoptosis. Gonocytes and early spermatogonia are the cell types that are 
vulnerable to this p53-trigged apoptosis, which results in a decrease in the 
size of the pool of germ-line stem cells. Amifostine fails to protect the germ 
cells against this cytotoxic insult.