Steroid biosynthesis and Leydig cell morphology in adult unilaterally cryptorchid rats.

Unilateral cryptorchidism was induced in newborn rats and when the rats reached adult age Leydig cell morphology and steroid biosynthesis were compared in scrotal and abdominal testes. The cell profile area of abdominal Leydig cells was reduced, the cytoplasm contained an increased number of lipid droplets and the endoplasmatic reticulum was more sparse than in scrotal Leydig cells. The intratesticular concentrations of progesterone, 20 alpha-dihydroprogesterone, 17 alpha-hydroxyprogesterone and testosterone were measured both basally and after LH stimulation. The synthesis of testosterone was subnormal in the abdominal testes. The data on basal steroid concentrations suggest a block at the 17 alpha-hydroxylase level, but observations after LH stimulation suggest that earlier steps are also involved. When studied in vitro the steroid biosynthesis in abdominal testes was also disturbed. The conversion mediated by 17 alpha-hydroxylase and 17 beta-ketosteroid reductase was lower and the conversion mediated by 20 alpha-dehydrogenase was higher in the abdominal testis. The reason for the disturbed steroid biosynthesis in abdominal testes is unknown. It may be related to the increased concentration of oestradiol in abdominal testes. Other possibilities are altered paracrine influence from the damaged tubules or changes in the microcirculation of the testis.