Immunocytochemical analysis of cells in the pars tuberalis of the rat hypophysis with antisera to hormones of the pars distalis.

The objective was to acquire evidence regarding the secretory capacity of cells in the pars tuberalis of the rat pituitary by the application of immunocytochemical staining. For this purpose the conjugated antibody and immunoglobulin-enzyme bridge techniques were utilized with antisera to the following hormones of the pars distalis: human somatotropin, human thyrotropin, human beta-melanotropin, ovine luteinizing hormone (LH), porcine beta17-39-corticotropin, and beta1-24-corticotropin. Only LH-containing cells were demonstrated. They were exceedingly rare in the cephalic pars tuberalis beneath the median eminence. The frequency of LH-cells was greater in the pars tuberalis associated with the infundibulum and increased distally. LH-cells were most common ventrolateral to the infundibular stem and occurred singly and in clusters. These results indicate that following hypophysectomy the portion of the pars tuberalis that remains in situ has the capacity to secrete only LH of all the pars distalis hormones.