[Dynamics of prolactin-I125 accumulation in the organs of lactating rats and its subcellular distribution in mammary tissue].

A study was made of the dynamics of prolactin-I125 accumulation in the kidneys, mammary gland and the liver of lactating rats in the course of 100 min. after the administration of the hormone. Absorption of the labeled prolactin occurred most intensively in the kidneys, where it splits. Iodides served as the principal radioactive product of prolactin-I125 splitting in the urine. The liver displayed no significant prolactin-binding activity. Prolactin-I125 accumulation in the mammary gland occurred at a constant rate. In this tissue labeled prolactin was localized outside the cells -- at first in the lymphatic and intercellular space and then -- in milk. The interval from the time of the hormone accumulation in the tissue to the appearance of radioactive products in milk was about 13 minutes. Prolactin-binding fragments of plasmatic membranes of the mammary gland cells were distributed in fractionation of this tissue by the method of differential centrifugation in the mitochondrial, lysosomal and microsomal fractions.