Differentiation of growth hormone‐ and prolactin‐containing acidophils with peroxidase‐labeled antibody

In order to verify the concept that growth hormone and prolactin are contained in two different populations of acidophils, sections of Bouin‐fixed rat hypophyses were stained immunochemically. For this purpose the histochemical demonstration of peroxidase was utilized after sequential application to the tissue section of rabbit antiserum to human growth hormone (or antiserum to rat prolactin) followed by application of peroxidase‐labeled sheep antiserum to rabbit gamma‐globulin. It was found that growth hormone cells and prolactin cells, when revealed immunochemically, corresponded structurally to cell types that could be differentiated with reasonable certainty in sections stained with the Masson trichrome procedure. When delineated immunochemically, growth hormone cells were larger and more densely arranged in the adult male than in the intact female; they exhibited little change in the female after ovariectomy. In contrast, prolactin cells were large and frequent in the female hypophysis but were small and less frequent in the male and in the female after ovariectomy. By double‐staining, growth hormone and prolactin cells were differentiated in the same section. It was concluded that (a) growth hormone and prolactin are contained in, and presumably secreted by, two different populations of acidophils; and (b) the Masson procedure permits a reasonably accurate differentiation of the two cell types.