Department of Physiology, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu 807-8555, Japan.
Peptides. 2010 Jun;31(6):1124-30. doi: 10.1016/j.peptides.2010.02.020. Epub 2010 Mar 7.
The expression of the relaxin-3 gene, detected as a new member of the insulin superfamily using human genomic databases, is abundantly present in the brain and testis. Intracerebroventricularly (icv) administered relaxin-3 stimulates food intake. Icv administered relaxin (identical to relaxin-2 in humans) affects the secretion of vasopressin and drinking behavior. Relaxin-3 partly binds relaxin family peptide receptor 1, which is a specific receptor to relaxin. Thus, we hypothesized that relaxin-3 would have physiological effects in the body fluid balance. However, the effects of relaxin-3 in the body fluid balance remain unknown. In the present study, we revealed that icv administered relaxin-3 induced dense Fos-like immunoreactivity (Fos-LI) in the rat hypothalamus and circumventricular organs including the organum vasculosum of the lamina terminalis, the median preoptic nucleus, supraoptic nucleus (SON), the subfornical organ (SFO) and the paraventricular nucleus (PVN), that are related to the central regulation of body fluid balance. Icv administered relaxin-3 (54, 180 and 540 pmol/rat) also induced a significant increase in c-fos gene expression in a dose-dependent manner in the SON, SFO and PVN. Further, icv administered relaxin-3 (180 pmol/rat) significantly increased water intake, and the effect was as strong as that of relaxin-2 (180 pmol/rat). These results suggest that icv administered relaxin-3 activates osmosensitive areas in the brain and plays an important role in the regulation of body fluid balance.
松弛素-3 基因的表达，作为使用人类基因组数据库检测到的胰岛素超家族的新成员，在大脑和睾丸中大量存在。脑室内（icv）给予松弛素-3 可刺激摄食。icv 给予松弛素（与人类的松弛素-2 相同）会影响血管加压素的分泌和饮水行为。松弛素-3 部分与松弛素家族肽受体 1 结合，该受体是松弛素的特异性受体。因此，我们假设松弛素-3 在体液平衡中具有生理作用。然而，松弛素-3 在体液平衡中的作用尚不清楚。在本研究中，我们发现脑室内给予松弛素-3 可诱导大鼠下丘脑和室周器官（包括终板血管器、正中视前核、视上核、穹窿下器和室旁核）中密集的 Fos 样免疫反应（Fos-LI），这些器官与体液平衡的中枢调节有关。脑室内给予松弛素-3（54、180 和 540 pmol/大鼠）也以剂量依赖性方式诱导 SON、SFO 和 PVN 中 c-fos 基因表达的显著增加。此外，脑室内给予松弛素-3（180 pmol/大鼠）可显著增加水的摄入，其作用与松弛素-2（180 pmol/大鼠）相当。这些结果表明，脑室内给予松弛素-3 激活了大脑中的渗透压敏感区，并在体液平衡调节中发挥重要作用。
