Immunocytochemical and morphometric investigations of mammotrophs, somatotrophs and somatomammotrophs in sheep pituitary cell cultures

Alterations occurring when sheep anterior pituitary cells are placed in culture for 4 days were studied using electron microscopy and immunogold labelling. The majority of cells present showed marked morphological changes during culture, with degranulation and development of extensive rough endoplasmic reticulum. The proportions of somatotrophs and mammotrophs, as identified by immunogold labelling, fell during culture. The majority (70%) of somatotrophs showed relatively little degranulation but the remainder were extensively degranulated after 4 days in culture, suggesting two subpopulations of this cell type. Conversely, most (80%) of the mammotrophs showed extensive degranulation after culture, but one-fifth remained heavily granulated, suggesting that mammotrophs too are heterogeneous. The proportion of cells labelling for both GH and prolactin (somatomammotrophs) increased during culture to about 3% of the cells present, compared with less than 0.2% of all cells before culture.