title: A 14-kilodalton prolactin-like fragment is secreted by the hypothalamo-neurohypophyseal system of the rat.
abstract: The recently described expression of the PRL gene, and the occurrence of a 14-kilodalton (kDa)PRL-like immunoreactive protein in the hypothalamo-neurohypophyseal system of the rat have raised the possibility that PRL variants are released from neurohypophyseal terminals into the blood. In this study, we investigated the local production of a hypothalamo-neurohypophyseal 14-kDa PRL-like protein by showing an independent origin from adenohypophyseal PRL. No 14-kDa PRL-like protein was detected in adenohypophyseal extracts by Western blots, whereas chronic hypophysectomy produced no change in the immunocytochemical detection of PRLs in supraoptic and paraventricular magnocellular neurons. In addition, a 14-kDa immunoreactive PRL-like protein was released into the medium by incubated neurohypophyseal lobes. Western blot analysis showed that significantly more of this 14-kDa protein was released into calcium-containing medium (1.8 mM) than into calcium-free medium. Furthermore, depolarizing concentrations of potassium (56 mM) increased by 3-fold the release of immunoreactive PRL by incubated hypothalamo-neurohypophyseal explants. In addition, a 14-kDa PRL-like antigen was detected in the circulation of the rat by Western blot analysis. These results are consistent with the local synthesis and calcium-dependent release of neurohypophyseal PRL-like proteins that include a predominant 14-kDa form.
authors.affiliation: Centro de Neurobiología, Universidad Nacional Autónoma de México, México D.F., México.
authors.forename: L
authors.initials: L
authors.lastname: Torner
authors.forename: S
authors.initials: S
authors.lastname: Mejía
authors.forename: F J
authors.initials: FJ
authors.lastname: López-Gómez
authors.forename: A
authors.initials: A
authors.lastname: Quintanar
authors.forename: G
authors.initials: G
authors.lastname: Martínez de la Escalera
authors.forename: C
authors.initials: C
authors.lastname: Clapp
mesh_terms: D000818:Animals; D015153:Blotting, Western; D005260:Female; D007031:Hypothalamus / Q000378:metabolism*; D007150:Immunohistochemistry; D008297:Male; D008970:Molecular Weight; D010904:Pituitary Gland, Posterior / Q000378:metabolism*; D011388:Prolactin / Q000097:blood / Q000378:metabolism*; D011817:Rabbits; D051381:Rats; D017208:Rats, Wistar
chemical_list: D011388:Prolactin