Hazlerigg D G, Barrett P, Hastings M H, Morgan P J
Molecular Neuroendocrinology Group, Rowett Research Institute, Aberdeen, Scotland, UK.
Mol Cell Endocrinol. 1996 Oct 14;123(1):53-9. doi: 10.1016/0303-7207(96)03900-7.
Evidence suggests that the pineal hormone melatonin modulates prolactin (PRL) secretion in part through direct effects on the anterior pituitary. However, high-affinity membrane receptors for melatonin are only found in the pars tuberalis (PT) of the anterior pituitary, whereas lactotrophs are confined to the pars distalis (PD). This study therefore sought to determine whether melatonin might have direct effects on the PD, through alternate pathways. Such a possibility had been suggested by recent reports of melatonin binding to members of the retinoid-related orphan nuclear receptor family (ROR/RZR). Expression of ROR(alpha)/RZR(alpha) isoforms was observed by reverse transcription PCR in the ovine PT and PD. Correspondingly unidentified nuclear proteins from these tissues showed binding to consensus DNA response elements for members of the ROR/RZR family. In contrast nuclear 2-[125I]iodomelatonin (IMEL) binding was not detectable in PD or PT extracts even at high ligand and tissue concentrations. Nevertheless, the conditions used allowed membrane and nuclear IMEL binding to be observed in PT and liver extracts, respectively. Overall these findings do not support the possibility of direct effects of melatonin on the adult PD, and by implication they reinforce the view that the melatonin-responsive PT is an intermediary in the control of PRL secretion.
有证据表明，松果体激素褪黑素部分通过对垂体前叶的直接作用来调节催乳素（PRL）的分泌。然而，褪黑素的高亲和力膜受体仅在前叶的结节部（PT）中发现，而催乳素细胞局限于远侧部（PD）。因此，本研究旨在确定褪黑素是否可能通过其他途径对远侧部产生直接作用。最近关于褪黑素与类视黄醇相关孤儿核受体家族（ROR/RZR）成员结合的报道提示了这种可能性。通过逆转录PCR在绵羊的结节部和远侧部观察到ROR(α)/RZR(α)亚型的表达。相应地，来自这些组织的未鉴定核蛋白显示与ROR/RZR家族成员的共有DNA反应元件结合。相比之下，即使在高浓度配体和组织的情况下，在远侧部或结节部提取物中也检测不到核2-[125I]碘褪黑素（IMEL）结合。然而，所使用的条件分别允许在结节部和肝脏提取物中观察到膜结合和核IMEL结合。总体而言，这些发现不支持褪黑素对成年远侧部有直接作用的可能性，这意味着它们强化了这样一种观点，即对褪黑素作出反应的结节部是催乳素分泌控制中的一个中间环节。
