title: Production of transferrin-like immunoreactivity by rat anterior pituitary and intermediate lobe.
abstract: Using a specific anti-rat transferrin (Tf) antiserum, Tf-like immunoreactivity (Tf-lir) was detected by immunostaining in intact rat pituitaries and in reaggregated pituitary cells cultured in serum-free medium. Tf-lir cells were present in the anterior pituitary (AP), and in the intermediate (IL) and neural lobes (NL). In the AP, Tf-lir cells were oval or polygonal. An unusual topographical distribution was found. Tf-lir cells mainly occurred as dense clusters in the lateral wings. In the central part of the AP, Tf-lir was found in flattened perisinusoidal cells. Double immunostaining for Tf and the different pituitary hormones showed that Tf-lir co-localized with some gonadotrophs and somatotrophs (7% and 3% of Tf-lir cells, respectively, in typical sections). No co-localization was seen with PRL, ACTH, TSH, or alpha-MSH. The distribution of Tf-lir cells and their cell shape completely differed from that of S-100-positive cells in the AP. In the IL, clusters of large stellate Tf-lir cells were found. Again, their distribution completely differed from S-100-positive cells. In the NL, diffuse staining was found. Double immunostaining of paraffin-embedded sections of reaggregate cell cultures of the AP did not reveal any co-localization of Tf-lir with ACTH, alpha-MSH, LH, FSH, TSH, GH, or PRL. In aggregates consisting of NL + IL cells, Tf-lir was located in clusters: no co-localization with ACTH or alpha-MSH could be demonstrated. Reaggregate cell cultures of AP and NL + IL secreted Tf-lir as measured by radioimmunoassay, at least during 21 days of culture. After metabolic labeling with [35S]-methionine and immunoprecipitation of [35S]-methionine-labeled material present in the culture medium of both AP and NL + IL aggregates with anti-Tf antiserum, a 35S-labeled substance was found, which on SDS-PAGE showed an apparent M(r) of approximately 78 KD, corresponding to the M(r) of rat Tf. The present data show that a specific population of cells of rat anterior pituitary is capable of synthesizing, storing, and secreting transferrin or a substance closely related to it. Cells different from melanotrophs and S-100 cells in the IL, as well as pituicytes in the NL, also appear to produce this material. We suggest that transferrin or a transferrin-like substance may have a local role in the transport of iron or other metals or may play a role as growth factor in the three lobes of the pituitary gland.
authors.affiliation: Laboratory of Cell Pharmacology, University of Leuven School of Medicine, Belgium.
authors.forename: D
authors.initials: D
authors.lastname: Tilemans
authors.forename: V V
authors.initials: VV
authors.lastname: Vijver
authors.forename: G
authors.initials: G
authors.lastname: Verhoeven
authors.forename: C
authors.initials: C
authors.lastname: Denef
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008715:Methionine; D010903:Pituitary Gland, Anterior / Q000378:metabolism*; D011233:Precipitin Tests; D011863:Radioimmunoassay; D051381:Rats; D017208:Rats, Wistar; D013462:Sulfur Radioisotopes; D014168:Transferrin / Q000096:biosynthesis* / Q000378:metabolism
chemical_list: D013462:Sulfur Radioisotopes; D014168:Transferrin; D008715:Methionine