Interaction of corticotropin-releasing factor (CRF) and alpha-helical CRF on rat neurointermediate lobes: in vitro studies.
Neurointermediate lobes (NILS) of the pituitary glands of adult male Sprague-Dawley rats were incubated in media in the presence of corticotropin-releasing factor (CRF), a stimulator of proopiomelanocortin (POMC) peptide release. Alpha-helical CRF, a peptide known to inhibit CRF induced POMC peptide release from the anterior pituitary, was incubated with NILS for a period of 90 min, to study its potential ability to modulate peptide release from the intermediate lobe. The alpha-helical peptide reduced beta-endorphin release from NILS, as measured by radioimmunoassay (RIA), when added for the entire incubation, or when added 30 min after start of the incubation period, with CRF present. Alpha-helical CRF alone reduced beta-endorphin release, as compared to control or CRF-treated lobes. Ultrastructural examination of intermediate lobes fixed at the end of incubations revealed a reduction in the numbers of Golgi-associated dense granules, an indicator of new peptide synthesis, in intermediate lobe tissue treated with alpha-helical CRF alone, both peptides together, or with CRF followed by alpha-helical peptide. The in vitro studies demonstrate the effectiveness of the antagonist peptide on intermediate lobe peptide secretion, thereby extending its effects to both POMC-secreting areas of the pituitary gland.
Saland
L C
LC
Department of Anatomy, University of New Mexico School of Medicine, Albuquerque.
Carr
J A
JA
Samora
A
A
Benavidez
S
S
Tejeda
D
D
D000818:Animals; D003346:Corticotropin-Releasing Hormone / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D003470:Culture Media; D003594:Cytoplasmic Granules / Q000648:ultrastructure; D006056:Golgi Apparatus / Q000648:ultrastructure; D008297:Male; D008854:Microscopy, Electron; D010446:Peptide Fragments / Q000494:pharmacology*; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D011333:Pro-Opiomelanocortin / Q000378:metabolism*; D011863:Radioimmunoassay; D051381:Rats; D011919:Rats, Inbred Strains; D001615:beta-Endorphin / Q000378:metabolism*
D003470:Culture Media; D010446:Peptide Fragments; D001615:beta-Endorphin; D011333:Pro-Opiomelanocortin; D003346:Corticotropin-Releasing Hormone; C045089:corticotropin releasing hormone (9-41)