IMMUNOCYTOCHEMICAL AND INSITU HYBRIDIZATION STUDIES OF PEPTIDYLGLYCINE-ALPHA-AMIDATING MONOOXYGENASE IN PITUITARY-GLAND

The pituitary gland contains high levels of pep-tidylglycine α-amidating monooxygenase (PAM) activity and mRNA. Using affinity-purified rabbit polyclonal antisera gen-erated to synthetic PAM peptides and PAM RNA probes, im-munocytochemical and in situ hybridization studies were con-ducted to determine the tissue disposition and cell types express-ing PAM in the adult male rat pituitary gland. PAM immunoreactivity was present at varying levels in nearly all of the anterior pituitary cells; one cell population stained intensely, while others stained moderately or weakly. These results corre-lated well with in situ hybridization studies that demonstrated high levels of PAM mRNA in a subpopulation comprising ap-proximately 10-15% of the anterior pituitary cells. Based upon immunocytochemistry, intermediate pituitary lobe cells were divided into an intensely stained and a moderately stained group. PAM staining was also present in neural lobe fibers. Immunocytochemical staining of serial pituitary tissue sections for PAM and other pituitary hormones demonstrated that the anterior pituitary cells intensely stained for PAM represented a subpopulation of the gonadotropes. PAM was also identified at moderate levels in corticotropes and at lower levels in sommatotropes and lactotropes. These results suggest that many anterior pituitary cells are capable of producing amidated peptides along with their major peptide hormone. © 1990 by The Endocrine Society.