The natural history of prolactin and GH secretion in mice with high and low incidence of mammary tumors.

Abstract

The serum and pituitary concentrations of GH and prolactin (PRL) in two strains of mice were compared between 20 and 250 days of age. The mice studied were of the C3H/St and C57BL/St strains, the incidence of spontaneous mammary tumors being high (∼90%in virgin females) in the former and low <1%) in the latter strain. Males and females of each strain were sacrificed by decapitation in groups of 8 to 16, at 20, 30, 35, 40, 60, 80, 100, 150, 200, and 250 (females only) days of age. The GH and PRL in the pituitary glands and sera were measured be specific, homologous radioimmunoassays. In general, C3H/St mice possessed more GH than did mice of the C57BL/St strain, both in serum and in the pituitary gland. Also, males in each strain had higher levels of the hormone than females. In relation to age, GH concentrations increased in the pituitary gland but decreased in serum between 20 and 40 days of age; following this period both constituents showed remarkable constancy with advancing age. Changes in PRL concentrations were more complex; the pituitary glands of C3H/St mice always contained more PRL than those of C57BL/St mice of the same sex, and the pituitaryglands of females in each strain had greater quantities than those of the respective males. In serum, however, C3H/St females had lower concentrations of PRL than C57BL/St females for 80 days but approached those of C57BL/St between 80 and 200 days. At 250 days, when serum PRL of the C57BL/St female declined significantly, that of the C3H/St remained relatively high. Male members of the C3H/St strain showed no difference in serumconcentrations of PRL from C57BL/St males for the first 80 days buthad substantially higher concentrations between 80–200 days. Further, in C3H/St mice there was no significantdifference between males and females in the concentrations of serum PRL,where as the average concentrations of PRL in sera of females of the C57BL/St strain were consistently 3–4 times higher than in males of this strain. Foster nursing of C57BL/St mice by C3H/St mothers increased theconcentrations of GH in the pituitary glands of members of both sexes and decreased the level of PRL from thatusually present in the sera of C57BL/St females around 70–80 days of age, suggesting an influence of some milk-borne factor(s) on the pattern of these hormones found in C3H/St mice in adult life. It is possible that the differences seen in the secretion of PRL andGH in the C3H/St strain, whether due to the mammary tumor virus or other strain characteristics, may relate to the higher incidence of mammary tumors in this strain. (Endocrinology94: 757, 1974)