MULTIPLE FACTORS WITH STEROIDOGENESIS-REGULATING ACTIVITY IN TESTICULAR INTERTUBULAR FLUID FROM NORMAL AND EXPERIMENTALLY CRYPTORCHID ADULT-RATS

Steroidogenesis-stimulating activity (SSA) was examined in testicular inter tubular fluid from normal, and short-term and long-term (up to 1 2 months) experimentally cryptorchid rats, using an in vitro Leydig ce ll bioassay based on testosterone production over 20 h in the presence of a maximum dose of human chorionic gonadotropin. Total fluid volume increased throughout the period of cryptorchidism, while intertubular testosterone concentrations declined. SSA from cryptorchid rats was s ignificantly greater (2- to 3-fold) than normal at all time-points; ho wever, the major increase in activity occurred within the fir st 4 wee ks after treatment. Similar concentrations of lipoproteins were recove red from both untreated and 4-week cryptorchid fluid by density ultrac entrifugation, although the bioactivity of the cryptorchid testis lipo protein fi action was 8-fold higher than the lipoprotein fraction from untreated testes. Moreover, removal of the lipoproteins led to a loss of SSA in the lipoprotein-deficient fraction of the intertubular flui d. Consequently, the in vitro bioassay conditions were modified by add ition of a constant level of serum lipoproteins to all assay wells. Em ploying the lipoprotein-supplemented bioassay, multiple stimulatory an d inhibitory activities were resolved by Sephadex G-100 gelfiltration in intertubular fluid from both normal and cryptorchid testes: (il an inhibitory activity eluting in the void volume (> 150 kDa), which decr eased after cryptorchidism; (ii) a stimulatory activity (40-80 kDa), w hich did not appear to be affected by cryptorchidism, (iii) an inhibit ory activity (20-40 kDa) which decreased after cryptorchidism, and (iv ) a stimulatory activity (12-20 kDa) which increased after cryptorchid ism. These results indicate that the increase in testicular SSA after, cryptorchidism is due to an increase in the proportion of stimulatory to inhibitory factors in intertubular fluid, and that both locally-pr oduced and serum-derived factors are involved.