Mechanisms of ion and acid-base regulation at the gills of freshwater fish.

G. G. Goss, S. F. Perry, C. M. Wood, P. Laurent

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Abstract

This review examines the branchial mechanisms utilized by freshwater fish to regulate internal acid-base status and presents a model to explain the underlying basis of the compensatory processes. Rainbow trout, Oncorhynchus mykiss, and brown bullhead, Ictalurus nebulosus, were examined under a variety of experimental treatments which induced respiratory and metabolic acid-base disturbances. Acid-base regulation was achieved by appropriate adjustments of Na+ and Cl- net fluxes across the gills which, in turn, were accomplished by variable contributions of three different branchial mechanisms: 1) differential changes in Na+ and Cl- diffusive effluxes, 2) changes in internal substrate (H+, HCO3-) availability, and 3) morphological adjustments to the gill epithelium. Differential diffusive efflux of Na+ over Cl- was involved only during periods of metabolic alkalosis. The importance of internal substrate availability was demonstrated using a two-substrate model. According to the model, ionic flux rates (J(in)Cl-, J(in)Na+) are determined not only by the concentration of the external ion (Na+, Cl-) but also by the concentration of the internal counterion (H+, HCO3-). This system provides for an "automatic negative feedback" to aid in the compensation of metabolic acid-base disturbances. Morphological alteration of the gill epithelia and the associated regulation of chloride cell (CC) fractional area is an essential third mechanism which is especially important during respiratory acid-base disturbances. Specifically, fish vary the availability of the CC associated Cl-/HCO3- exchange mechanism by physical covering/uncovering of CCs by adjacent pavement cells.

Original languageEnglish
Pages (from-to)143-159
Number of pages17
JournalJournal of Experimental Zoology
Volume263
Issue number2
StatePublished - Aug 15 1992

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ASJC Scopus subject areas

  • Animal Science and Zoology

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Goss, G. G., Perry, S. F., Wood, C. M., & Laurent, P. (1992). Mechanisms of ion and acid-base regulation at the gills of freshwater fish. Journal of Experimental Zoology, 263(2), 143-159.