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[3-Me-His2]-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 adenohyp...

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Published in:Neuropeptides (Edinburgh) 2000-04, Vol.34 (2), p.83-88
Main Authors: Bourdais, J., Romero, F., Uriostegui, B., Cisneros, M., Joseph-Bravo, P., Charli, J.-L.
Format: Article
Language:English
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Summary: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 500nM dopamine (DA) for 24h prior to treatments. We observed a rapid increase of PP II activity when 100nM [3-Me-His2]-TRH, a TRH agonist, was added at removal of DA. PPII activity was maximal after 20min of treatment and reduced to time 0 activity at 30min. Dopamine withdrawal alone, slightly and transiently, modified the enzyme activity: an initial activation at 15min was followed by a transient inhibition at 20min. The specific contribution of [3-Me-His2]-TRH in this paradigm was a transient enhancement of PP II activity. If DA was not removed, [3-Me-His2]-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.
ISSN:0143-4179
1532-2785
DOI:10.1054/npep.2000.0796