Bihormonal cells producing gonadotropins and prolactin in a rat pituitary tumor cell line (RC-4B/C).

Using single hormone-staining immunocytochemical methods, we have recently characterized a novel cell line, RC-4B/C, established from an aged male rat pituitary adenoma. This cell line contained all known anterior pituitary cell types including gonadotropes. Gonadotropin-releasing hormone receptors were also present. A recent re-examination of the cell types using single hormone stains showed that the cell line underwent an alteration in the percentage of different cell types as compared to the data obtained 2 years ago. The proportion of follicle-stimulating hormone-beta (FSH beta), luteinizing hormone-beta (LH beta), prolactin (PRL), and adrenocorticotropic hormone cells increased significantly (p less than or equal to 0.001), while the proportion of growth hormone (GH), and thyrotropin-beta cells did not change. Dual staining of the monolayers showed that the cell line contained many bihormonal cells producing FSH beta + LH beta, FSH beta + PRL and LH beta + PRL. The proportion of bihormonal FSH beta + LH beta and FSH beta + PRL cells was preponderant over monohormonal cells, while the proportion of bihormonal LH beta + PRL cells was in the same range as that of monohormonal cells. Preliminary data with dual labeling also revealed the presence of GH and PRL in the same cell, but complete absence of a combination such as FSH beta + GH. No search for the presence of other bihormonal or multihormonal cells was performed. In short, our data show that the majority of the cells in the cell line RC-4B/C contain FSH beta, LH beta and PRL and that among these cells many bihormonal cells are present.