Morphological responses of the rainbow trout (Oncorhynchus mykiss) gill to hyperoxia,base (NaHCO3) and acid (HCl) infusions |
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Authors: | Greg G. Goss Chris M. Wood Pierre Laurent Steve F. Perry |
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Affiliation: | (1) Department of Biology, University of Ottawa, 30 Marie Curie, Ottawa, Ontario, Canada, K1N 6N5;(2) Department of Biology, McMaster University, 1280 Main St. West, Hamilton, Ontario, Canada, K1N 6N5;(3) Laboratoire de Morphologie Fonctionelle et Ultrastructurale des Adaptations, CNRS, 23 Rue de Loess, F-67037 Cedex, Strasbourg, France;(4) Hospital for Sick Children, Division of Cell Biology, 555 University Avenue, Toronto, Ontario, M5G 1X8 |
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Abstract: | Marked morphological responses occur in the gills of freshwater rainbow trout in response to experimental acid-base disturbance and these responses play an important role in acid-base correction. Compensated respiratory acidosis induced by 70h exposure to environmental hyperoxia (elevated water PO2) caused a 33% decrease in branchial chloride cell fractional surface area (CCFA). Metabolic alkalosis induced by normoxic recovery (6h) from hyperoxia (72h) caused a 50% increase in CCFA, whereas metabolic alkalosis induced by infusion (19h) of NaHCO3 caused a 70% rise. However, the largest increase (135%) in CCFA was seen in response to infusion (19h) of HCl. NaCl infusion had no effect. A particular goal was to assess the relative importance of changes in CCFA vs. changes in internal substrate (HCO3–) availability in regulating the activity of the branchial Cl–/HCO3– exchange system. For each of the experimental treatments, the accompanying blood acid-base status and branchial transport kinetics (Km, Jmax) for Cl– uptake had been determined in earlier studies. In the present study, a positive linear relationship was established between CCFA and JCl–max in individual control fish in the absence of an acid-base disturbance. By reference to this relationship, observed changes in JCl–max during metabolic acid-base disturbances were clearly due to changes in both CCFA and internal substrate levels (plasma [HCO3–]) with the two factors having approximately equal influence. |
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Keywords: | fish chloride cell morphology kinetics Km Jmax acid-base |
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