DIFFERENCE IN MAMMARY GLAND SUSCEPTIBILITY TO PROLACTIN BETWEEN A HIGH AND A LOW MAMMARY TUMOR STRAINS OF MICE

As one step of determining whether the superiotriy of C3H/He to C57BL/6 in mammary gland growth and lactation performance depends principally upon the susceptibility of the mammary gland to mammotrophic hormones or the quantities of these hormones acting on the gland or both, the differences in mammary growth and secretion between isologous pituitary grafted C3H/He and C57BL/6 mice and those between (C57BL/6×C3H/He) F1 hybrids given pituitary grafts from either of their parent strains were investigated. While C3H/He was much more remarkable than C57BL/6 in mammary growth and secretion by isologous pituitary grafts, there was little difference in these phenomena between F1 hybrids with pituitary grafts from C3H/He or C57BL/6. These results indicate that little strain difference exists in the quantity of prolactin secreted from the grafts and that the gland of C3H/He has higher susceptibility to prolactin than that of C57BL/6. Further, the importance of mammary susceptibility to prolactin for its development and function should be emphasized.