In vitro binding of radioiodinated human placental lactogen to murine mammary gland

In vitro binding of radioiodinated human placental lactogen (125I-HPL) to homogenates of the mouse mammary gland was studied. The hormone binding components were susceptible to proteolytic enzymes. Differential centrifugation studies revealed the existence of hormone binding components in fractions of mammary gland homogenates sedimentable at 800g, 10,000g and 100,000g. The binding was affected by incubation time and hormone concentration. Theophylline increased the binding of 125I-HPL to mammary gland. Comparative studies on binding capacity of mammary gland of mice resistant and susceptible to spontaneous development of breast cancer suggest that mammary glands of C3H (Jax) mice have significantly higher binding capacities than those of C57 BL