Identification by plaque assays of a pituitary cell type that secretes both growth hormone and prolactin.

Sequential application of reverse hemolytic plaque assays for GH and PRL revealed the presence of individual pituitary cells that released both hormones. These dual cells accounted for approximately one third of all GH and/or PRL secretors in 24-h pituitary cultures derived from male rats. Additional studies in which a different version of the plaque assay and double-staining immunocytochemistry were applied separately to dispersed pituitary cells from males yielded results that were virtually identical. These results suggest that mammosomatotropes, cells that secrete both GH and PRL, may exist in pituitaries of normal rats.