Vargas M A, Cisneros M, Joseph-Bravo P, Charli J L
Departamento de Genetica y Fisiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de Mexico, Cuernavaca.
Endocrine. 2000 Dec;13(3):267-72. doi: 10.1385/endo:13:3:267.
Thyrotropin-releasing hormone (TRH) is inactivated by a narrow specificity ectopeptidase, pyroglutamyl aminopeptidase II (PPII), in the proximity of target cells. In adenohypophysis, PPII is present on lactotrophs. Its activity is regulated by thyroid hormones and 17beta-estradiol. Studies with female rat adenohypophyseal cell cultures treated with 3,3',5'-triiodo-L-thyronine (T3) showed that hypothalamic/paracrine factors, including TRH, can also regulate PPII activity. Some of the transduction pathways involve protein kinase C (PKC) and cyclic adenosine monophosphate (cAMP). The purpose of this study was to determine whether T3 levels or gender of animals used to propagate the culture determine the effects of TRH or PKC. PPII activity was lower in cultures from male rats. In cultures from both sexes, T3 induced the activity. The percentages of decrease due to TRH or PKC were independent of T3 or gender; the percentage of decrease due to cAMP may also be independent of gender. These results suggest that T3 and hypothalamic/paracrine factors may independently control PPII activity in adenohypophysis, in either male or female animals.
促甲状腺激素释放激素（TRH）在靶细胞附近被一种特异性狭窄的外肽酶——焦谷氨酸氨肽酶II（PPII）失活。在腺垂体中，PPII存在于催乳细胞上。其活性受甲状腺激素和17β-雌二醇调节。对用3,3',5'-三碘-L-甲状腺原氨酸（T3）处理的雌性大鼠腺垂体细胞培养物的研究表明，包括TRH在内的下丘脑/旁分泌因子也能调节PPII活性。一些转导途径涉及蛋白激酶C（PKC）和环磷酸腺苷（cAMP）。本研究的目的是确定用于培养细胞的动物的T3水平或性别是否会决定TRH或PKC的作用。雄性大鼠培养物中的PPII活性较低。在两性的培养物中，T3均可诱导其活性。TRH或PKC导致的活性降低百分比与T3或性别无关；cAMP导致的活性降低百分比可能也与性别无关。这些结果表明，在雄性或雌性动物中，T3和下丘脑/旁分泌因子可能独立控制腺垂体中的PPII活性。
