[Degradation of prolactin 125-I in the mammary gland of lactating rats].

Prolactin-125I metabolism in the mammary gland of lactating rats was studied; the hormone was injected intraperitoneally. Radioactive products accumulated by the mammary gland tissue were extracted with isotonic medium. Tissue extracts, blood serum and milk were analyzed by gel filtration on Sephadex G-200. The Blood displayed a gradual reduction of prolactin-125I content as a result of its splitting in the organs and binding with blood proteins; as to the mammary gland--there occurred accumulation of the products of prolactin-125I degradation. Some hormone was inactivated losing immunological properties without any significant changes in the molecular weight. Besides, the mammary gland displayed an intensive accumulation of the products of prolactin-125I splitting in the other organs and in the gland proper. Radioactivity accumulated in the milk was mainly referred to the products of prolactin-125I degradation. There was also shown the presence of immunologically active prolactin-125I in the milk.