Progesterone decreases tyrosine hydroxylase phosphorylation state and increases protein phosphatase 2A activity in the stalk-median eminence on proestrous afternoon.
Progesterone decreases tyrosine hydroxylase phosphorylation state and increases protein phosphatase 2A activity in the stalk-median eminence on proestrous afternoon.
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DOI：
10.1677/joe-09-0335
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发表时间：
2010-02
期刊：
影响因子：
--
通讯作者：
Arbogast LA
中科院分区：
文献类型：
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作者：
Liu B;Arbogast LA
孕激素（P4）在动情前期下午的升高与酪氨酸羟化酶（TH）的去磷酸化和茎正中隆起（SME）TH活性的降低有关，这有助于大鼠动情前期的催乳素激增。在本研究中，我们研究了P4对TH活性和磷酸化状态，以及cAMP水平和蛋白磷酸酶2A（PP 2A）的活性和数量的时间过程中，在SME在发情前期的上午和下午。P4（7.5mg/kg，sc）在动情前期下午给药1h内降低TH活性和Ser-31和Ser-40的TH磷酸化状态，而早晨给药1h对TH无影响。P4处理1h后，SME中PP 2A活性增强，但PP 2A催化亚基数量没有变化，而P4处理对PP 2A活性和数量没有影响。SME中的环AMP水平在1小时P4处理下没有变化。在P4处理后5 h，TH活性和磷酸化状态下降，与P4处理的上午和下午组的血浆催乳素的增加一致。P4处理5小时大鼠SME中的PP 2A活性无变化。我们的数据表明，P4对结节漏斗多巴胺能神经元的作用涉及至少两个组件。一个更快的（1小时）P4的影响，只从事对proestrous下午可能涉及激活PP 2A。较长的P4对结节漏斗多巴胺能神经元的作用在发情前期的上午和下午都很明显，可能涉及一种共同的，尚未确定的机制。
The progesterone (P4) rise on proestrous afternoon is associated with dephosphorylation of tyrosine hydroxylase (TH) and reduced TH activity in the stalk-median eminence (SME), which contributes to the proestrous prolactin surge in rats. In the present study, we investigated the time course for P4 effect on TH activity and phosphorylation state, as well as cAMP levels and protein phosphatase 2A (PP2A) activity and quantity, in the SME on proestrous morning and afternoon. P4 (7.5 mg/kg, sc) treatment on proestrous afternoon decreased TH activity and TH phosphorylation state at Ser-31 and Ser-40 within 1h, whereas morning administration of P4 had no 1h effect on TH. PP2A activity in the SME was enhanced after P4 treatment for 1h on proestrous afternoon without a change in PP2A catalytic subunit quantity, whereas P4 treatment had no effect on PP2A activity or quantity on proestrous morning. Cyclic AMP levels in the SME were unchanged with 1h P4 treatment. At 5h after P4 treatment, TH activity and phosphorylation state declined coincident with an increase in plasma prolactin in both P4-treated morning and afternoon groups. PP2A activity in the SME was unchanged in 5h P4-treated rat. Our data suggest that P4 action on tuberoinfundibular dopaminergic neurons involves at least two components. A more rapid (1h) P4 effect engaged only on proestrous afternoon likely involves activation of PP2A. The longer P4 action on tuberoinfundibular dopaminergic neurons is evident on both the morning and afternoon of proestrus and may involve a common, as yet unidentified, mechanism.