Studies on testicular function iii. Effects of fsh, lh, testosterone and dihydrotestosterone on restoration and maintenance of testicular-specific lactate dehydrogenase activity in the hypophysectomized rat

Hypophysectomy of the adult male rat depressed the activity of testicular-specific lactate dehydrogenase (LDH-X). Groups of rats were treated with FSH (F), LH (L) or testosterone (T) alone or in combination after 32 days of post-hypophysectomy regression (restoration experiment) for a further 32 days or with F, T or dihydrotestosterone (D) alone or in combination from 2 days after hypophysectomy (maintenance experiment) for 30 daysLDH-X activity per milligram of protein was restored to normal by the hormonal combinations FT and LT while F, L, or T given alone or the FL and FLT combinations were ineffective. However, the total LDH-X activity per testis was only partially restored by the hormonal combinations FT, LT and FLT.In the maintenance experiment LDH-X activity per milligram of protein was maintained by all hormonal treatments except D, while the total LDH-X activity per testis was completely maintained by the FT hormonal combination. All other hormonal treatments except F alone maintained the activity of this isoenzyme above the level in the hypophysectomized rat.The restoration and maintenance of LDH-X activity in the testis of the hypophysectomized ratwas successful with those combinations of hormones that were also able to restore or maintain the numbers of late primary spermatocytes and spermatids. Thus, the level of LDH-X activity in the testis is dependent on the presence of late primary spermatocytes and spermatids and hence this enzyme is a good marker for the production of these cells in the rat testis