2025-08-21 東京大学,国立遺伝学研究所,岡山大学
図1:海水から淡水への環境水変化に応答して、尿量が増加するしくみ
<関連情報>
- https://www.aori.u-tokyo.ac.jp/research/news/2025/20250821.html
- https://www.aori.u-tokyo.ac.jp/research/news/2025/files/20250821_summary_0.pdf
- https://www.cell.com/iscience/fulltext/S2589-0042(25)01535-4
広塩性赤エイにおける低浸透圧環境への適応のための広範な尿産生 Extensive urine production in euryhaline red stingray for adaptation to hypoosmotic environments
Naotaka Aburatani ∙ Wataru Takagi ∙ Marty Kwok-Shing Wong ∙ … ∙ Waichiro Godo ∙ Tatsuya Sakamoto ∙ Susumu Hyodo
iScience Published:August 20, 2025
DOI:https://doi.org/10.1016/j.isci.2025.113274
Highlights
- Our new device enables continuous urine sampling from a conscious red stingray
- Red stingray can increase the urine volume by 87-fold in low salinity conditions
- Urine output increases via enhanced glomerular filtration and reduced water reabsorption
- Segment-specific aquaporin regulation contributes to diuresis and osmolyte retention
Summary
Maintaining water balance is a prerequisite for all organisms. Euryhaline elasmobranchs face the severest water-influx potential in fresh water (FW), as they retain high concentrations of urea even in hypotonic environments. To elucidate how they overcome this osmotic challenge, we assessed urine output in conscious euryhaline red stingrays (Hemitrygon akajei). Following acclimation to 5% diluted seawater, the stingrays increased urinary output by 87-fold—the greatest change observed in vertebrates—partly due to 6.8-fold increase in glomerular filtration rate (GFR). In the nephron, expressions of Aquaporin-1 (Aqp1), Aqp3, and Aqp15 were strongly downregulated in FW, indicating that tubular diuresis bridges the gap between GFR and final urine volume. Meanwhile, FW-acclimation upregulated Aqp1 and Aqp4 in the distinct bundle structure, which promotes urea reabsorption. Euryhaline elasmobranchs resolve the huge osmotic challenge of FW by excreting massive amounts of water and retaining osmolytes including urea through coordinated regulation of GFR and Aqp expressions.
