Immunocytochemical localization of prohormone convertases PC1 and PC2 in the anuran pituitary gland: subcellular localization in corticotrope and melanotrope cells.
Specific antisera against mammalian prohormone convertases PC1 and PC2 have been used to examine, light-immunocytochemically, the distribution of these enzymes in the pituitary gland of five different species of anuran amphibians (Rana catesbeiana, Bufo japonicus formosus, Xenopus laevis, Rana brevipoda porosa, and Buergeria japonica). A differential pattern of immunoreactivity of PC1 and PC2 was found among these species. Only PC1 was found in the corticotrope cells of the pars distalis in R. catesbeiana, B. japonicus formosus, and X. laevis. Only PC2 was observed in these cells in B. japonica, whereas both PC1 and PC2 were present in these cells in R. brevipoda porosa. PC2 immunoreactivity was always observed in melanotrope cells in the pars intermedia of all of the species, but it coexisted with PC1 immunoreactivity only in R. catesbeiana and X. laevis. The nerve fibers and terminals in the pars nervosa in all of the species were intensely immunopositive with both PC1 and PC2 antibodies. Immunoelectron microscopy on B. japonicus formosus and B. japonica, by means of double-labeling with gold particles of different sizes, revealed that almost all the adrenocorticotropin-positive secretory granules in the corticotrope cells and alpha-melanophore-stimulating-hormone-positive secretory granules in the melanotrope cells were also labeled with either PC1 or PC2 antibodies. This study suggests that PC1 and PC2 are involved in the intracellular proteolytic cleavage of proopiomelanocortin in amphibian pituitary glands, a situation similar to that proposed for mammals.
Kurabuchi
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Department of Histology, School of Dentistry, The Nippon Dental University, Tokyo 102, Japan.
Tanaka
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D000324:Adrenocorticotropic Hormone / Q000032:analysis; D000818:Animals; D001001:Anura / Q000502:physiology*; D016282:Aspartic Acid Endopeptidases / Q000032:analysis*; D002025:Bufonidae; D003594:Cytoplasmic Granules / Q000201:enzymology / Q000648:ultrastructure; D007150:Immunohistochemistry; D016253:Microscopy, Immunoelectron; D010902:Pituitary Gland / Q000166:cytology / Q000201:enzymology* / Q000648:ultrastructure; D045706:Proprotein Convertase 2; D043484:Proprotein Convertases; D011892:Rana catesbeiana; D011898:Ranidae; D013045:Species Specificity; D013381:Subtilisins / Q000032:analysis*; D014982:Xenopus laevis; D000521:alpha-MSH / Q000032:analysis
D000521:alpha-MSH; D000324:Adrenocorticotropic Hormone; D043484:Proprotein Convertases; D013381:Subtilisins; D045706:Proprotein Convertase 2; D016282:Aspartic Acid Endopeptidases