[3-Me-His(2)]-TRH combined with dopamine withdrawal rapidly and transiently increases pyroglutamyl aminopeptidase II activity in primary cultures of adenohypophyseal cells.
TRH is hydrolyzed by pyroglutamyl aminopeptidase II (PP II), a highly specific ecto-enzyme which is localized on the surface of lactotrophs. To study whether PP II activity may be rapidly regulated during a burst of prolactin secretion, we used an in vitro model in which primary cultures of adenohypophyseal cells were incubated with 500 nM dopamine (DA) for 24 h prior to treatments. We observed a rapid increase of PP II activity when 100 nM [3-Me-His(2)]-TRH, a TRH agonist, was added at removal of DA. PPII activity was maximal after 20 min of treatment and reduced to time 0 activity at 30 min. Dopamine withdrawal alone, slightly and transiently, modified the enzyme activity: an initial activation at 15 min was followed by a transient inhibition at 20 min. The specific contribution of [3-Me-His(2)]-TRH in this paradigm was a transient enhancement of PP II activity. If DA was not removed, [3-Me-His(2)]-TRH was ineffective. These data demonstrate that during in vitro conditions that mimic a suckling episode, adenohypophyseal PP II activity is rapidly and reversibly adjusted.
Bourdais
J
J
Departamento de Genetica y Fisiologia Molecular, Instituto de Biotecnologia, Universidad Nacional Autonoma de Mexico, Cuernavaca, Mor, Mexico.
Romero
F
F
Uriostegui
B
B
Cisneros
M
M
Joseph-Bravo
P
P
Charli
J L
JL
D000626:Aminopeptidases / Q000378:metabolism*; D000818:Animals; D002478:Cells, Cultured; D004298:Dopamine / Q000494:pharmacology*; D005260:Female; D010903:Pituitary Gland, Anterior / Q000166:cytology / Q000201:enzymology*; D011761:Pyrrolidonecarboxylic Acid / Q000031:analogs & derivatives; D051381:Rats; D017208:Rats, Wistar; D013973:Thyrotropin-Releasing Hormone / Q000819:agonists* / Q000031:analogs & derivatives* / Q000494:pharmacology*
C014109:thyrotropin-releasing hormone, 3-Me-; D013973:Thyrotropin-Releasing Hormone; D000626:Aminopeptidases; C023166:pyroglutamyl-peptidase II; D011761:Pyrrolidonecarboxylic Acid; D004298:Dopamine