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Response of Beagle Mammary Dysplasias to Various Hormone Supplements in Vitro¹

Department of Veterinary Anatomy, University of California, Davis, California 95616

The canine mammary tumor system is receiving increasing attention as a model system for drug testing and for experimental study of basic mammary biology. In order to contribute to this model system, the hormone sensitivity of three types of canine preneoplastic lesions was identified morphologically on the basis of in vitro responses of organ-cultured explants to various hormone supplements. Dysplastic tissues were selected in vivo on the basis of their difference in hormone responsiveness. Differential hormone sensitivity of dysplastic from normal tissues persisted in vitro. Three types of tissues were studied: ductal connective tissue dysplasias, hyperplastic alveolar lobular dysplasias, and explants of an adenoma. All maintained their structure in vitro, independent of the hormone supplement provided. Secretion in alveolar lesions was hormone-independent. Secretion in the adenofibroma was hormone responsive, both to supplements that promote secretion in normal tissues of beagles (cortisol, mammotropin, and insulin; and estradiol, progesterone, cortisol, mammotropin, somatotropin, and insulin) and to two hormone combinations to which normal tissues are unresponsive (mammotropin, somatotropin, and insulin; and estradiol, progesterone, cortisol, and insulin).

Exploitation of in vitro techniques promises to be a valuable tool for exploring the progression from normal to neoplastic in canine mammary tissues.

¹ Supported in part by USPHS Grant FRO-5457, USPHS Research Contract 43-69-33, and Atomic Energy Commission Contract AT (04-3) 472. Based in part on a dissertation submitted in partial fulfillment of the requirements for a Ph.D. in Anatomy, University of California, Davis, Calif. 95616.

² Present address: Department of Cell Biology, Baylor College of Medicine, Houston, Texas 77030.

Received 12/21/76. Accepted 3/23/77.