Preputial separation as an external sign of pubertal development in the male rat.

The normal occurrence of preputial separation was determined in 4 groups of rats by daily attempts after 30 days of age to manually retract the prepuce with gentle pressure. In Group 1 blood samples were collected via cardiac puncture and steroid determinations made. Group 2 animals were castrated and silastic implants of steroids placed. Group 3 was tested for mature motile sperm in the caput epididymus; 1/2 of the Group 4 rats were handled daily from Days 1 to 21. The mean ages of preputial separation in the 4 groups were 39 42 44 and 45 days of age just preceding the appearance of mature sperm in the caput epididymis. Preputial separation occurred prior to the significant increase in circulating androgen levels by Day 51 as measured by radioimmunoassay. Castration as late as Day 35 blocked preputial separation demonstrating that separation was dependent on the continued presence of low-level androgen. Silastic implants of testosterone or dihydrotestosterone but not estradiol reversed the effects of castration. Handling neonatal males daily prior to weaning significantly delayed preputial separation and was correlated with significantly lower circulating levels of androgen and luteinizing hormone at 45 days of age. Preputial separation may be used as an index of change in peripubertal androgen secretion.(Authors modified)