The effect of flutamide on testicular descent in rats examined by scanning electron microscopy.

The effect of prenatal flutamide exposure on testicular descent was investigated by using scanning electron microscopy (SEM) in prenatal and postnatal rats. In 20-day-old fetal rats, SEM showed no significant difference in the degree of gubernacular development or testicular descent relative to the kidney between flutamide-treated (74.5 +/- 2.2 U) and control rats (73.3 +/- 1.5 U); however, there was significant inhibition in oestrogen-treated rats (44.3 +/- 2.2 U) (P < .001). (The distance between the kidney and the bladder neck was standardized to 100 U.) In 5-day-old rats, SEM showed inhibited downward growth of the processus vaginalis in flutamide-treated rats. The length of processus vaginalis below the inguinal ligament was 32.8 +/- 2.4 U in flutamide-treated rats and 51.7 +/- 1.8 U in controls (P < .001). In 30- to 35-day-old mature rats, the frequency of cryptorchidism was 41.3% for flutamide-treated rats and 0% for controls (P < .001). Some cryptorchid testes were located in the lower abdominal cavity (10.9%); others were in the suprainguinal position (26.1%) or on the line of descent in the inguinal region (4.3%). In the flutamide-treated group, no testes were located in the posterior abdominal cavity, near the kidney. These results suggest that transabdominal descent of the testis is independent of androgen action, but that androgens control inguinoscrotal descent of the testis by regulating gubernacular migration and the growth of the processus vaginalis.