The effects of hyperprolactinemia on the activity of 3β-hydroxysteroid dehydrogenase (3β-HSD) in rat testis were studied during excessive 17β-estradiol (E2) administration. Without E2 treatment, 3β-HSD activity did not change significantly in moderate hyperprolactinemic rats (756 ± 179 ng/ml). However, this enzyme activity was significantly decreased in marked hyperprolactinemic rats (3612 ± 1090 ng/ml) compared to that in control rats (45.4 ± 6.2 ng/ml). Under the excessive E2 administration, this enzyme activity was insignificantly decreased in slight hyperprolactinemic rats (218 ± 42 ng/ml1 and inhibited in moderate hyperprolactinemic rats (566 ± 77 ng/ml) as refer to control level.
It may be concluded that inhibition of 3β-HSD activity in testis due to the excess administration of estrogen is promoted by the transplantation of MtT/F84 which produces prolactin at the limited level
