[Comparative studies of prolactin, estrogen, progesterone and androgen receptor levels in human breast cancers].

A receptor for lactogenic hormones (prolactin of several species and human growth hormone) was characterized in crude plasma membrane preparations of adult female rat liver. The binding of 125J-labeled prolactin to receptors was specific, saturable, reversible, and of high affinity (Kd = 0.23 x 10(-10)M). The maximum amount of prolactin specifically bound to liver of untreated female rats was 45 fmol/mg protein, whereas no specific prolactin binding was detected in plasma membrane preparations of adult male or immature rats. With this assay, a specific and reversible binding of ovine prolactin was detected in plasma membrane preparations of 25 human breast cancers, ranging from 2-29% of total activity. The estrogen-, progesterone- and androgen receptor content was determined in the breast cancer specimens using the dextran-coated charcoal method. Specimens with the highest specific prolactin binding showed the lowest steroid receptor concentrations, but no significant correlation between estrogen-, progesterone-, androgen-, and prolactin receptor content and other prognostic factors was observed in our series. We conclude, that steroid and prolactin receptors are expressed independently in human breast cancer.