Emerson C H, Alex S, Braverman L E, Safran M S
Endocrinology. 1981 Nov;109(5):1375-9. doi: 10.1210/endo-109-5-1375.
TRH, a PRL secretogogue, is metabolized to histidyl-proline diketopiperazine (HPD) in brain and plasma. HPD has been reported to inhibit PRL secretion in vitro. In the present study, intravascular pulse injections or infusions of HPD were carried out in the rat to determine whether HPD affected 1) TRH-induced PRL secretion, 2) the PRL proestrous surge, 3) the PRL surge in the ovariectomized, estrogen-primed rat and 4) pimozide-induced hyperprolactinemia. HPD had no effect on TRH-induced PRL secretion in estrogen-primed male rats when administered in molar ratios of 1:1.5 to 1:150 (TRH:HPD). The infusion of 1 microgram/min HPD for 360 min to rats before and during the proestrous PRL surge did not inhibit or augment PRL secretion, nor was there any influence of pulse injections of HPD on PRL secretion during the proestrous surge. HPD did not influence spontaneous PRL surges in the ovariectomized estrogen-primed rat. Finally, HPD, given with pimozide and again 2 days later, did not influence the PRL surge after pimozide administration or the elevated serum PRL concentrations noted 2 days after pimozide treatment. Despite the promising in vitro data demonstrating that the TRH metabolite, HPD, has PRL inhibitory factor activity, this study does not support the concept that HPD is a physiological PRL inhibitory factor.
促甲状腺激素释放激素（TRH）是一种催乳素分泌刺激因子，在脑和血浆中代谢为组氨酰 - 脯氨酸二酮哌嗪（HPD）。据报道，HPD在体外可抑制催乳素分泌。在本研究中，对大鼠进行了血管内脉冲注射或输注HPD，以确定HPD是否会影响：1）TRH诱导的催乳素分泌；2）发情前期催乳素激增；3）去卵巢并用雌激素预处理的大鼠中的催乳素激增；4）匹莫齐特诱导的高催乳素血症。当以1:1.5至1:150（TRH:HPD）的摩尔比给药时，HPD对雌激素预处理的雄性大鼠中TRH诱导的催乳素分泌没有影响。在发情前期催乳素激增之前和期间，以1微克/分钟的速度向大鼠输注HPD 360分钟，既没有抑制也没有增强催乳素分泌，发情前期激增期间HPD的脉冲注射对催乳素分泌也没有任何影响。HPD对去卵巢并用雌激素预处理的大鼠中的自发性催乳素激增没有影响。最后，与匹莫齐特一起给药以及2天后再次给药的HPD，对匹莫齐特给药后的催乳素激增或匹莫齐特治疗2天后观察到的血清催乳素浓度升高没有影响。尽管体外数据显示TRH代谢产物HPD具有催乳素抑制因子活性，但本研究不支持HPD是一种生理性催乳素抑制因子的概念。
