Prolactin Binding to Rat Mammary Tumor Tissue

Abstract

Summary

Specific binding of ¹²⁵I-ovine prolactin was measured in mammary tumors from rats given 7, 12 dimethylbenzanthra-cene. A significant correlation was noted between the binding of prolactin to par-ticulate membrane fragments in the total microsomal pellet and the growth response of these tumors to the administration of prolactin, that is the tumors showing the greatest response to prolactin also bound the greatest amount of ¹²⁵I-ovine prolactin (r = 0.69). There was a negative correlation between the average growth response of all tumors in one rat and the amount of ¹²⁵I-ovine prolactin specifically bound to liver membranes of that animal (r = — 0.69). This or a similar method of determining prolactin dependence may be useful in assessing prolactin responsiveness in human breast cancer.

We are indebted to Dr. Paul Schurr, the Upjohn Company, (Kalamazoo, Michigan) for providing the DMBA emulsion. Ovine prolactin was supplied by the National Pituitary Agency, NIAMDD. The secretarial help of Mrs. Judy Harapiak and the excellent technical assistance of Miss Teresa Cody are greatly appreciated. This research was supported by the Medical Research Council of Canada (MT-1867, USPHS Child and Human Development Grant HD-0172-08 and the National Cancer Institute NCI E-C-72-26 (HGF); National Cancer Institute CA-10771 and NIAMD AM 04784 (JM).