Mammary Lobulo-Alveolar Growth Induced by Anterior Pituitary Hormones in Adreno-Ovariectomized and Adreno-Ovariectomized-Hypophysectomized Rats.

Summary 1. Mature virgin female Car-worth rats of the CFN strain were adreno-ovariectomized and were then injected thrice daily for 10 days with saline, 2 mg bovine STH, 30 I.U. ovine prolactin, 20 mg bovine anterior pituitary powder, or with a combination of 1.33 mg bovine STH and 20 I.U. ovine prolactin. Treatment with STH and prolactin together or with anterior pituitary powder induced moderate to extensive mammary duct and lobulo-alveolar growth, while treatment with prolactin and STH alone induced mainly duct and end bud development. 2. Two groups of rats were hypophysectomized and 3 days later were adreno-ovariectomized. They were then injected thrice daily for 10 days with saline or with a combination of 1.33 mg STH and 20 I.U. prolactin for 10 days. The latter treatment induced extensive duct and moderate lobulo-alveolar growth. Completeness of ovariectomy, adrenalectomy and hypophysectomy was checked in all rats upon autopsy. Sixteen additional adreno-ovariectomized rats which were given tap water failed to survive more than 19 days. 3. It is concluded that under conditions of this experiment, full mammary duct and lobulo-alveolar growth was induced by combined treatment with bovine STH and ovine prolactin in the absence of ovaries and adrenals. Addendum. Histological examination of stained mammary sections from adreno-ovariectomized rats treated with prolactin and STH failed to reveal any secretory activity. The authors are indebted to Mr. T. F. Hopkins for performing the hypophysectomies and to Mr. C. S. Nicoll for the photographs.