. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 112 DAVID H. EVANS ET AL. BLOOD Cl. SEA WATER Cl . No - No FIGURE 2. Current model for the mechanisms of Na+ and Cl extrusion by the branchial epithelium of marine fishes. Redrawn from Silva et al. (1977). See text for details and supporting evidence. species apparently maintain TEPs distinctively below the equilibrium potential for Na+ (see reviews by Kirschner, 1979, 1980, and Evans, 1980b). If Na+ is in elec- trochemical equilibrium then the ionic substitution experiments which indicated that Na+/K+ exchange may be taking
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 112 DAVID H. EVANS ET AL. BLOOD Cl. SEA WATER Cl . No - No FIGURE 2. Current model for the mechanisms of Na+ and Cl extrusion by the branchial epithelium of marine fishes. Redrawn from Silva et al. (1977). See text for details and supporting evidence. species apparently maintain TEPs distinctively below the equilibrium potential for Na+ (see reviews by Kirschner, 1979, 1980, and Evans, 1980b). If Na+ is in elec- trochemical equilibrium then the ionic substitution experiments which indicated that Na+/K+ exchange may be taking place may also possibly be explained by TEP changes. This has proved to be the case in some species (Potts and Eddy, 1973; Kirschner et al., 1974) but not in others (Evans, 1975; Maetz and Pic, 1975; Evans and Cooper, 1976). In addition, Na+/Na+ exchange diffusion which was first described by Motais et al. (1966) has now been shown to be a TEP effect in some species (Potts and Eddy, 1973; Kirschner et al., 1974) but not others (Evans, 1975; Maetz and Pic, 1975; Evans and Cooper, 1976). Thus, whole-animal studies on the mechanisms for salt extrusion in sea water have left us with the rather unsatisfying conclusion that some animals may be extruding net amounts of Na+ and Cl and others may only need to extrude Cl~ (the TEP of all marine teleosts examined to date is distinctly different from the equilibrium potential for Cl~; Evans, 1980b). Studies of the mechanisms of Cl~ extrusion by whole animals have indicated that it is sensitive to the external K+ concentration (Epstein et al., 1973) and to the external HCO3 but not OH~ concentration (Kormanik and Evans, 1979), and inhibited by injection of thiocy- anate (Epstein et al., 1973). In addition, both Na+ and Cl~ efflux are inhibited by injection of the Na+-K+ activated ATPase inhibitor ouabain into the blood of the eel, Anguilla rostrata (Silva et al., 1977). Since it had been shown that Na+-K+ activated ATPase is actually locat
Size: 1192px × 2097px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
