Acclimation to Copper by Rainbow Trout,Salmo gairdneri: Physiology

Abstract

Juvenile rainbow trout (Salmo gairdneri) were exposed to 55 μg copper∙L−1 for 28 d and then transferred to uncontaminated water for 7 d. Whole body sodium concentration and sodium uptake (Jin) were measured at weekly intervals; Jin was measured at various Na+ concentrations and kinetic parameters estimated. After 24 h of copper exposure, the maximum rate of sodium uptake (Jmax) was inhibited by 55%, the affinity for sodium (Km) reduced by 49%, and whole body Na+ decreased by about 12.5%. After 7 d of exposure, whole body Na+ had returned to control values, but Jmax was still inhibited by 41%. Recovery of whole body Na+ occurred largely by a reduction of sodium efflux (Jout). Both Jmax and Km continued to recover until day 28, at which time Jin had returned to control values. We conclude that acclimation to sublethal copper depends on changes in both Na+ transport and permeability.

Acclimation to Cu in fathead minnows: Does age influence the response?

“…Several studies have shown that acclimated fish maintain whole-body Na + concentrations relative to unexposed fish. Laurén and McDonald (1987) found that upon initial exposure to subacute Cu concentrations, a reduction in whole-body Na + occurred. However, 7 d after initiation of the exposure, whole-body Na + returned to pre-exposure concentrations.…”

“…Acclimation to Cu arises via recovery of ionoregulatory function at the gills where physiological alterations occur to restore Na + influx (Laurén and McDonald, 1987;McGeer et al, 2000). Several studies have shown that acclimated fish maintain whole-body Na + concentrations relative to unexposed fish.…”

“…Several toxicological studies have shown that fish exposed to sublethal levels of Cu are capable of acclimation (Dixon and Sprague, 1981;Buckley et al, 1982;Benson and Birge, 1985;Laurén and McDonald, 1987;Wilson and Taylor, 1992). Acclimation to Cu has been defined as the ability to tolerate typically lethal Cu exposures while maintaining normal physiological function (McDonald and Wood, 1993).…”

“…Whole-body Na + serves as one such indicator, as acclimation to Cu is typically accompanied by recovery of Na + ionoregulation and subsequently whole-body Na + levels (Laurén and McDonald, 1987;McGeer et al, 2000). Several studies have utilized wholebody Na + concentrations to determine the mechanisms underlying Cu tolerance and toxicity (Laurén and McDonald, 1987;Grippo and Dunson,1991;Croke and McDonald, 2002;Kolok et al, 2002). Generally, it would be expected that if one biological indicator (e.g., survival) indicated tolerance, then other biological indicators (e.g., whole-body Na + ) would also be indicative of tolerance (Croke and McDonald, 2002).…”

Kinetics of Cu2+ inhibition of Na+K+-ATPase

“…Free C u2+ inhibits N a + /K +-ATPase activity in a variety of cell types and in a variety of species [9][10][11][12][13]. Although the toxic action o f Cu2+ is mainly attributed to covalent binding o f C u2+ to functional sulfhydryl (-SH) groups of membrane proteins and enzymes [14][15][16][17], including N a + /K +-ATPase [18][19][20], the kinetics of C u 2+ interaction with N a + /K +-ATPase are flawed by the fact that, in these studies, the total concentration of copper rather than the free C u 2+ concentrations was con sidered.…”