Analysis of prolactin and growth hormone production in the MtT/F4 transplantable pituitary tumor by the reverse hemolytic plaque assay.

The reverse hemolytic plaque assay (RHPA) was used to detect hormone secretion from normal pituitary cells and from the transplantable MtT/F4 pituitary tumor cells. Aliquots of the same cell suspensions were analyzed by immunocytochemistry (ICC). Normal pituitaries had more growth hormone (GH)-producing cells than tumors when analyzed by both the RHPA and ICC. However, the MtT/F4 tumor had significantly more prolactin (PRL)-secreting cells. Mammosomatotropic (MS) cells, which produced both PRL and GH, were identified in both normal and tumorous pituitaries with the RHPA and ICC. A combined procedure of RHPA followed by ICC staining on the same slide also revealed MS cells in both normal and tumorous pituitary cells, although the percentage of MS with this technique was less than with the other two methods. These results show that MS cells from a significant population of cells in the MtT/F4 tumor and that the RHPA and ICC can be used to study the regulation of this cell type.