Colocalization of luteinizing hormone and serotonin in secretory granules of mammalian gonadotrophs.
Previous studies have demonstrated the uptake of exogenous and storage of endogenous 5-hydroxytryptamine (5-HT) in parenchymal cells of the anterior pituitary. The present experiments were undertaken to test the hypothesis that the endogenous 5-HT of the anterior lobe of the pituitary is costored with beta-luteinizing hormone (beta-LH) within the same secretory granules of gonadotrophs. Electron microscope immunocytochemistry was used to detect 5-HT and beta-LH immunoreactivities in the anterior pituitary glands of mice and bats. Primary antisera generated in different species of animals to these two antigens were localized with appropriate species-specific secondary antisera coupled to colloidal gold particles of different sizes. This enabled 5-HT and beta-LH immunoreactivities to be demonstrated simultaneously on ultrathin sections of fixed anterior lobe tissue mounted on electron microscope (EM) grids. In both bats and mice 5-HT immunoreactivity, identified by immunostaining of beta-LH, was found in gonadotrophs, and in no other cell type. Within gonadotrophs about 25% of the secretory granules were labeled by antisera to both 5-HT and beta-LH, although 100% of granules reacted with the antiserum to B-LH. No secretory granules were found that were immunostained only by the antiserum to 5-HT. It is concluded that endogenous 5-HT may be a normal constituent of mammalian gonadotrophs and that it is colocalized with beta-LH in at least a subset of the secretory granules of these cells. It cannot yet be concluded that gonadotrophs synthesize 5-HT as well as taking it up from the ambient medium.(ABSTRACT TRUNCATED AT 250 WORDS)
Payette
R F
RF
Gershon
M D
MD
Nunez
E A
EA
D000818:Animals; D000911:Antibodies, Monoclonal; D000937:Antigen-Antibody Reactions; D002685:Chiroptera; D003594:Cytoplasmic Granules / Q000032:analysis / Q000378:metabolism*; D006046:Gold; D007986:Luteinizing Hormone / Q000032:analysis / Q000378:metabolism*; D051379:Mice; D008815:Mice, Inbred Strains; D008854:Microscopy, Electron; D010903:Pituitary Gland, Anterior / Q000032:analysis / Q000378:metabolism* / Q000648:ultrastructure; D011817:Rabbits; D012701:Serotonin / Q000032:analysis / Q000378:metabolism*; D013194:Staining and Labeling
D000911:Antibodies, Monoclonal; D012701:Serotonin; D006046:Gold; D007986:Luteinizing Hormone