RESTORATION OF TESTICULAR TRANSFERRIN, INSULIN-LIKE GROWTH-FACTOR-I (IGF-1), AND SPERMATOGENESIS BY EXOGENOUSLY ADMINISTERED PURIFIED FSH AND TESTOSTERONE IN MEDICALLY HYPOPHYSECTOMIZED RATS

To investigate the relation between testicular transferrin and insulin -like growth factor-1 (IGF-I) secreted by Sertoli cells and the differ entiation of germ cells in the rat, testosterone and/or purified FSH w as administered to rats medically hypophysectomized by an LH-RH agonis t. Spermatogenesis was quantitatively analyzed and concentrations of i ntratesticular transferrin and IGF-1 were measured by radioimmunoassay s. The last step of spermatogenesis was quantitatively restored by com bined administration of testosterone and purified FSH. intratesticular IGF-1 concentrations were significantly increased by combined adminis tration of testosterone and purified FSH. From these observations, it is surmised that IGF-1 may have a stimulatory effect on the last step of spermatogenesis.