Secondary changes in the scrotal testis in experimental unilateral cryptorchidism

Unilateral cryptorchidism was induced in under 2-day-old Wistar rat pups. A control group of rats underwent sham operation at the same age. The animals were killed at intervals from 5 to 120 days, both testes were excised, weighted, and processed for histological examination, morphometric measurement of the seminiferous tubules, and DNA flow cytometry. There was no difference in weight, Johnsen score, and tubular size between the scrotal testis of cryptorchid animals and control testes at any age. Significant decreases in all of these parameters occurred in the undescended testis from 30 days when compared with the scrotal testis in cryptorchid animals and controls. Using flow cytometry to measure changes in the DNA ploidy of the cells of the seminiferous epithelium during spermatogenesis, a significant decrease in the haploid population of cells occurred in the scrotal testis of cryptorchid animals at 40 days. This difference continued into adult life (P less than .005). Flow cytometry demonstrates a secondary decrease in spermatogenesis in the scrotal testis in experimental unilateral cryptorchidism.