A 14-kilodalton prolactin-like fragment is secreted by the hypothalamo-neurohypophyseal system of the rat.
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.
Torner
L
L
Centro de Neurobiología, Universidad Nacional Autónoma de México, México D.F., México.
Mejía
S
S
López-Gómez
F J
FJ
Quintanar
A
A
Martínez de la Escalera
G
G
Clapp
C
C
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
D011388:Prolactin