Effects of Prolactin (PRL) on Pituitary and Testicular Function in Mice with Hereditary PRL Deficiency

Abstract

Hereditary dwarf mice (Snell dwarf, dw/dw and Ames dwarf, dfldf) are genetically prolactin-deficient and sterile. Treatment with prolactin (PRL) stimulates testicular growth and activity, and induces fertility in these animals. To elucidate the mechanism of this action of PRL, and to identify the possible physiological functions of this hormone during sexual maturation, we have examined the effects of treating male dwarf mice with PRL on plasma and pituitary levels of LH and FSH, on the concentration of testosterone (T) in testes and plasma, and on T production in response to hCG in vitro. Both Snell and Ames male dwarf mice had a significantly lower concentration of FSH in the pituitary and the peripheral plasma, and of LH in the pituitary, than did the normal adult males of the same strain. Treatment with ovine PRL, or with a PRL-producing ectopic homograft of the anterior pituitary from a normal animal, produced a significant elevation in plasma FSH levels in male dwarf mice of both strains. The same in vivo treatments also resulted in a significant increase in the capacity of the dwarf mouse testis to produce testosterone in vitro in the presence of hCG. In the course of normal sexual maturation, PRL may increase the responsiveness of the testis to LH and stimulate the release of FSH from the pituitary.