title: Effect of hypercapnia on intracellular pH regulation in a rainbow trout hepatoma cell line, RTH 149.
abstract: Fish exposed to elevated water CO(2) experience a rapid increase in blood CO(2) levels (hypercapnia), resulting in acidification of both intra- and extra-cellular compartments. While the mechanisms associated with extracellular pH regulation have been well explored, much less is known about intracellular pH (pH(i)) regulation. There is great interest in developing non-animal models for research. One such model is the rainbow trout hepatoma cell line (RTH 149), which has been used to study a wide range of topics; however, no studies have investigated its potential use in pH(i) regulation. Employing the pH-sensitive fluoroprobe BCECF, the present study examined pH(i) regulation in RTH 149 under normocapnia and during extracellular acidification induced by either elevated CO(2) or 1 M HCl. During exposure to hypercapnia, RTH 149 cells were acidified without recovery as long as the elevated CO(2) was maintained. In addition, rates of pH(i) recovery from NH(4)Cl-induced acidosis were significantly lower in cells exposed to hypercapnia or HCl compared to that in normocapnic cells, indicating that elevated CO(2) indirectly impeded pH(i) recovery through a reduction in pH(e) and/or pH(i). Moreover, pH(i) regulation in RTH 149 was EIPA-sensitive, suggesting that an NHE may be involved. Overall, RTH 149 may have the potential for identifying transporters likely to play a role in pH(i) regulation in fish. However, it should not be used as a complete replacement for in vivo studies, especially to quantify acid-base regulatory ability at whole animal level, since RTH 149 appeared to have enhanced pH(i) recovery rates relative to primary hepatocytes.
authors.affiliation: Department of Zoology, University of British Columbia, 6270 University Boulevard, Vancouver, BC, V6T 1Z4, Canada. huynh@zoology.ubc.ca
authors.forename: Khuong Tuyen
authors.initials: KT
authors.lastname: Huynh
authors.forename: Daniel W
authors.initials: DW
authors.lastname: Baker
authors.forename: Robert
authors.initials: R
authors.lastname: Harris
authors.forename: John
authors.initials: J
authors.lastname: Church
authors.forename: Colin J
authors.initials: CJ
authors.lastname: Brauner
mesh_terms: D000138:Acidosis / Q000378:metabolism / Q000662:veterinary*; D000818:Animals; D002245:Carbon Dioxide / Q000378:metabolism; D045744:Cell Line, Tumor; D005393:Fish Diseases / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D006935:Hypercapnia / Q000378:metabolism / Q000473:pathology / Q000662:veterinary*; D007425:Intracellular Membranes / Q000378:metabolism*; D008954:Models, Biological; D017686:Oncorhynchus mykiss / Q000378:metabolism*
chemical_list: D002245:Carbon Dioxide