Vesicular release of prolactin from preformed prolactin granules is stimulated by soluble factor(s) from the anterior pituitary of lactating rats.
This study demonstrates that conditioned media (CM) from the anterior pituitary gland (AP) of lactating rats contains soluble factors that promote in vitro prolactin (PRL) release from the pituitary glands of male rats. CM-induced PRL release was confirmed by polyacrylamide gel electrophoresis, ELISA and bioassay. In cultured AP cells challenged with CM, increased intracellular staining with the dye FM1-43 was observed, suggesting vesicular PRL release and subsequent endocytosis. The percentage and hormone content of PRL-containing cells but not of growth hormone-containing cells increased in cultured male AP cells when exposed to CM. When the release of PRL, prelabeled with [3H] leucine for 30 min to 24 h was examined, no stimulatory effect of CM was observed, suggesting that released PRL originates from hormone synthesized more than 24 h earlier. Accordingly, the PRL content of mature granules from male pituitary tissues decreased after CM treatment. These findings were confirmed by electron microscopy immunogold PRL labeling. Treatment with inhibitors of protein synthesis or vesicle trafficking between the endoplasmic reticulum and the Golgi complex did not prevent the stimulatory effect of CM on PRL release. However, blockage of traffic to the plasma membrane completely abolished the effect of CM. These results suggest that CM from the AP of lactators contains soluble factor(s) capable of inducing rapid vesicular release of PRL in the male AP, which originates from preformed, mature granules by mechanisms independent of protein synthesis.
Huerta-Ocampo
Icnelia
I
Departamentos de Neurobiología Celular y Molecular, Instituto de Neurobiología, Campus UNAM, Juriquilla-Querétaro, México.
Fiordelisio
Tatiana
T
Díaz
Nestor
N
Navarro
Nilda
N
Castilla
Alejandra
A
Cárabez
Alfonso
A
Aguilar
Manuel B
MB
Morales
Teresa
T
Hernández-Cruz
Arturo
A
Mena
Flavio
F
D000818:Animals; D000831:Animals, Newborn; D001681:Biological Assay / Q000379:methods; D002478:Cells, Cultured; D017077:Culture Media, Conditioned / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005260:Female; D007774:Lactation; D007930:Leucine / Q000378:metabolism; D008297:Male; D046529:Microscopy, Electron, Transmission; D010903:Pituitary Gland, Anterior / Q000737:chemistry / Q000166:cytology / Q000187:drug effects; D011388:Prolactin / Q000378:metabolism*; D011726:Pyridinium Compounds / Q000378:metabolism; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D022142:Secretory Vesicles / Q000187:drug effects* / Q000648:ultrastructure; D014316:Tritium / Q000378:metabolism
D017077:Culture Media, Conditioned; C073804:FM1 43; D011726:Pyridinium Compounds; D000644:Quaternary Ammonium Compounds; D014316:Tritium; D011388:Prolactin; D007930:Leucine