THE ROLE OF PROLACTIN IN THE REGULATION OF TESTIS FUNCTION: THE EFFECTS OF PROLACTIN AND LUTEINIZING HORMONE ON THE PLASMA LEVELS OF TESTOSTERONE AND ANDROSTENEDIONE IN HYPOPHYSECTOMIZED RATS

Abstract

SUMMARY: Testosterone and androstenedione levels in the plasma of hypophysectomized rats were measured by a protein-binding method (sensitivity 150 pg testosterone; precision, 10%). Testosterone levels in the plasma of saline-treated hypophysectomized rats were undetectable (P < 0·05). Administration of prolactin ± LH (same doses) increased testosterone levels to 5·07 ± 0·51 ng/ml which is significantly higher than when LH was given alone and exceeds testosterone levels in intact adult males (4·12 ± 0·60 ng/ml). Androstenedione levels in the plasma of saline-treated hypophysectomized rats were, in contrast to testosterone levels, very high and averaged 3·37 ± 0·60 ng/ml. This level is higher than that in saline-treated intact controls (1·89 ± 0·36 ng/ml). Treatment with prolactin, LH or prolactin + LH induced insignificant changes in androstenedione levels which were 1·80 ± 0·33, 2·02 ± 0·28 and 4·22 ± 0·75 ng/ml, respectively. The ratio testosterone: androstenedione was calculated to be 0·37 ± 0·08 in the prolactin-treated group, 0·76 ± 0·20 in the LH-treated group and 1·47 ± 0·64 in the prolactin + LH-treated group compared with 2·36 ± 0·28 in intact control males.