Abstract
The National Institute of Arthritis, Metabolism and Digestive Diseases antirat prolactin antiserum, used widely for radioimmunoassay of rat prolactin, was used in the unlabeled antibody-peroxidase-antiperoxidase complex method for the ultrastructural immunocytochemical staining of rat prolactin cells. Sections were exposed to antiprolactin antiserum (1:400-1:100,000) or to antiovine luteinizing hormone antiserum (1:1,000) for 3 min or 4 or 48 hr. Specificity of prolactin staining was demonstrated by the absence of immunologic staining of other pituitary cells and by negative results with prolactin cells when normal serum or antiovine luteinizing hormone antiserum was used. Intensity of prolactin staining was directly related to the concentration and duration of exposure to antiprolactin antiserum. Prolactin secretion granules, located peripherally or within Golgi regions, were uniformly stained. Immunologic staining for prolactin was not observed within cisternae of the endoplasmic reticulum. These results show that the National Institute of Arthritis, Metabolism and Digestive Diseases antirat prolactin antiserum is specific for prolactin by ultrastructural immunocytochemical criteria and that antiserum dilutions appropriate for radioimmunoassay can be used in immunologic localization studies.