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Prolactin Receptors in 7,12-Dimethylbenz(a)anthracene-induced Mammary Tumors Following Endocrine Ablation¹

Department of Medicine, University of Texas Health Science Center, San Antonio, Texas 78284

We have determined the effect of ovariectomy and hypophysectomy on prolactin receptors in 7,12-dimethylbenz(a)anthracene-induced mammary tumors. Growing tumors from intact rats show a wide range in the number of prolactin receptors. Ovariectomy causes a slight (30%) decrease in receptors regardless of whether tumors regress or continue to grow, while the affinity of the receptor for prolactin remains unchanged. Hypophysectomy, which causes a prompt 10-fold decrease in prolactin receptors in rat liver, causes only a slight reduction in prolactin receptors in tumors from these same animals. We conclude that autonomous and ovariectomy responsive 7,12-dimethylbenz(a)anthracene-induced mammary tumors cannot be distinguished on the basis of prolactin receptor sites and that endocrine regulation of prolactin receptors is distinctly different in normal liver and neoplastic mammary tissue.

¹ This investigation was supported by USPHS Grants CA-11378 and CB 23862, American Cancer Society Grant BC-23, and the Robert Welch Foundation.

² Recipient of NIH Research Fellowship CA 04004. Present address: Department of Biochemistry, St. Jude Children's Research Hospital, Memphis, Tenn. 38101.

³ To whom requests for reprints should be addressed.

Received 6/ 1/76. Accepted 8/ 3/76.