Regulation of apical H+-ATPase activity and intestinal HCO3−secretion in marine fish osmoregulation

• DOI: 10.1152/ajpregu.00059.2011
• Publication Date: 2011-08-25T03:52:42Z
• Authors: S. Guffey; A. Esbaugh; M. Grosell
• Keywords: Osmoregulation; Apical membrane; Bicarbonate; Acid–base homeostasis

The absorption of Cl(-) and water from ingested seawater in the marine fish intestine is accomplished partly through Cl(-)/HCO(3)(-) exchange. Recently, a H(+) pump (vacuolar-type H(+)-ATPase) was found to secrete acid into intestinal lumen, it may serve titrate luminal HCO(3)(-) facilitate further exchange, especially posterior intestine, where adverse concentration gradients could limit expressed all segments gill tissue gulf toadfish (Opsanus beta) maintained natural seawater. After acute transfer 60 ppt salinity, expression increased 20-fold intestine. In agreement with these observations fourfold-increased H(+)-ATPase activity animals acclimated salinity. Interestingly, Na(+)-K(+)-ATPase elevated anterior gill, but not Apical secretion by isolated mounted Ussing chambers fitted pH-stat titration systems after acclimation hypersalinity titrating >20% secreted bicarbonate. addition, net base hypersalinity-acclimated ∼70% dependent on serosal HCO(3)(-). Protein localization immunohistochemistry confirmed presence vacuolar-type apical region enterocytes. These results show that pump, plays an important role hypersaline osmoregulation likely has significant effects accumulation lumen and, therefore, continued water.