Characterization of Mammotrophs Separated From the Human Pituitary Gland

Human pituitary tissues from 27 patients and 7 persons post mortem were dissociated into single cell suspensions. On the average, 23% of the cells were mammotrophs. The concentration of prolactin in these suspensions averaged 3.8 ng/1,000 cells. After cell separation by velocity sedimentation at unit gravity, mammotrophs and other cell types were enriched twofold to threefold. The separated mammotrophs retained structural integrity at light and electron microscopic levels. In eight separation experiments, cells recovered from different gradient regions were assayed for intracellular prolactin levels. In cells from “normal” subjects, 8.5% of the prolactin recovered from the gradient was associated with large mammotrophs, whereas in patients with breast cancer, 28% of the hormone was associated with large mammotrophs. The number of mammotrophs recovered from this gradient region (beyond fraction 6) was doubled in breast cancer (2 expts). These mammotrophs showed areas of hypertrophied Golgi and endoplasmic reticulum. Culture of the separated cells from 1 patient with diabetes and 2 patients with breast cancer for 21 days showed that mammotrophs in the upper gradient fractions (diabetic) secreted seven times more hormone than those in the lower regions, whereas those mammotrophs from patients with breast cancer that fell to the lower gradient regions secreted 15 times more prolactin than did those in the upper regions. These data suggest that pituitaries of patients with breast cancer contain a small pool (10–20%) of hypertrophied mammotrophs that have the potential for significant secretory activity in vitro.