Abstract
The binding sites of antisera (anti) to the beta (beta) subunits of rat follicle-stimulating hormone (rFSH), rat luteinizing hormone (rLH), and rat thyroid-stimulating hormone (rTSH) have been localized in rat anterior pituitaries by immunocytochemistry using light and electron microscopy. With the light microscope, LHbeta and FSHbeta were found in the same cells, which were violet after the alcian blue-periodic acid Schiff (AB-PAS) staining. TSHbeta was found in polygonal or stellate cells that were blue after AB-PAS. With the electron microscope, the thyrotropic cells contained very small secretory granules. LHbeta and FSHbeta were found in various types of cells (types A and B and their intermediate forms), which had previously been identified as gonadotropic cells. On serial ultrathin sections using the postembedding method the same cells and even some granules inside these cells were stained by both anti-rLHbeta and anti-rFSHbeta. A comparison of binding sites of anti-rLHbeta was performed using the preembeeding and the postembeeding methods. Antigenicity was observed on secretory granules whatever the method used. However, binding sites of anti-rLHbeta were detected inside the cisternae of the rough endoplasmic reticulum only with the preembedding method.