Centre of Marine Sciences (CCMar), Universidade do Algarve, Campus de Gambelas, 8005-139 Faro, Portugal.
Int J Mol Sci. 2018 Apr 4;19(4):1072. doi: 10.3390/ijms19041072.
In marine fish, high epithelial intestinal HCO₃ secretion generates luminal carbonate precipitates of divalent cations that play a key role in water and ion homeostasis. The present study was designed to expose the putative role for calcium and the calcium-sensing receptor (CaSR) in the regulation of HCO₃ secretion in the intestine of the sea bream ( L.). Effects on the expression of the CaSR in the intestine were evaluated by qPCR and an increase was observed in the anterior intestine in fed fish compared with unfed fish and with different regions of intestine. CaSR expression reflected intestinal fluid calcium concentration. In addition, anterior intestine tissue was mounted in Ussing chambers to test the putative regulation of HCO₃ secretion in vitro using the anterior intestine. HCO₃ secretion was sensitive to varying calcium levels in luminal saline and to calcimimetic compounds known to activate/block the CaSR i.e., R 568 and NPS-2143. Subsequent experiments were performed in intestinal sacs to measure water absorption and the sensitivity of water absorption to varying luminal levels of calcium and calcimimetics were exposed as well. It appears, that CaSR mediates HCO₃ secretion and water absorption in marine fish as shown by responsiveness to calcium levels and calcimimetic compounds.
在海洋鱼类中，高上皮肠道 HCO₃分泌生成二价阳离子的腔碳酸盐沉淀，在水和离子稳态中起着关键作用。本研究旨在探讨钙和钙敏感受体（CaSR）在调节海鲈（L.）肠道 HCO₃分泌中的潜在作用。通过 qPCR 评估了 CaSR 在肠道中的表达情况，与未喂食鱼和肠道不同区域相比，喂食鱼的前肠中观察到 CaSR 表达增加。CaSR 表达反映了肠道流体钙浓度。此外，将前肠组织安装在 Ussing 室中，使用前肠在体外测试 HCO₃分泌的潜在调节作用。HCO₃分泌对腔生理盐水不同钙水平敏感，并且对已知激活/阻断 CaSR 的钙敏感受体化合物敏感，即 R 568 和 NPS-2143。随后在肠囊中进行实验，以测量水吸收，并暴露水吸收对腔钙水平和钙敏感受体化合物的敏感性。似乎 CaSR 介导了海洋鱼类的 HCO₃分泌和水吸收，这表现为对钙水平和钙敏感受体化合物的反应性。
