The Interaction of Environmental Calcium and Low pH on The Physiology of the Rainbow Trout, Salmo Gairdneri

Abstract

Adult rainbow trout, acclimated to external calcium concentrations ranging from 60–5700 μequiv/1, were exposed to pH 4.0-4.1 for 44 h. Initially, this exposure provoked massive net losses of sodium and chloride across the gills which arose through a combination of an inhibition of active transport and, more importantly, a stimulation in diffusional efflux. Subsequently, ion losses declined substantially, largely due to a rapid decline in passive efflux but also to a slower, partial recovery in sodium transport. External calcium concentration was virtually without effect on ion fluxes either prior to or following acid exposure but had a definite effect during acid exposure. This effect was initially upon the ratio of C1− to Na+ loss and later upon the degree of inhibition of sodium and chloride transport. Possible mechanisms to explain the complex interactions of calcium and pH are proposed.

The role of environmental calcium in the extreme acid tolerance of northern banjo frog (Limnodynastes terraereginae) larvae

“…In acid-naïve L. terraereginae, the high rate of net Na + efflux was exacerbated in the presence of low [Ca 2+ ] e , indicating a protective effect of [Ca 2+ ] e on epithelial junction integrity. This is consistent with previous studies showing that [Ca 2+ ] e plays a significant role in determining Na + efflux rates with low pH exposure in a range of fish and amphibian larvae (Cummins, 1988; Freda and Dunson, 1984; Freda et al, 1991; Gascon et al, 1987; Gonzalez and Dunson, 1989; Gonzalez et al, 1998; Kullberg et al, 1993; Kumai et al, 2011; McDonald and Rogano, 1986; McDonald et al, 1983; Meyer et al, 2010; Riesch et al, 2015). However, environmental Ca 2+ was only beneficial for controlling Na + efflux up to a point: exposure of larvae to 250 μmol L -1 [Ca 2+ ] e did not further reduce net Na + fluxes beyond that of larvae exposed to control (50 μmol L -1 ) levels.…”

“…] e has been shown to ameliorate the effects of low pH on epithelial integrity in some fish and amphibian species (Dalziel et al, 1986;Matsuo and Val, 2002;McDonald et al, 1983;Meyer et al, 2020). This may be because low [Ca…”

“…] e plays a significant role in determining Na + efflux rates with low pH exposure in a range of fish and amphibian larvae (Cummins, 1988;Freda and Dunson, 1984;Freda et al, 1991;Gascon et al, 1987;Gonzalez and Dunson, 1989;Gonzalez et al, 1998;Kullberg et al, 1993;Kumai et al, 2011;McDonald and Rogano, 1986;McDonald et al, 1983;Meyer et al, 2010;Riesch et al, 2015). However, environmental Ca…”

“…Environmental [Ca 2+ ] is essential to maintaining the integrity of the epithelial TJ (Schneeberger and Lynch, 1992). Increased [Ca 2+ ] e has been shown to ameliorate the effects of low pH on epithelial integrity in some fish and amphibian species (Dalziel et al, 1986; Matsuo and Val, 2002; McDonald et al, 1983; Meyer et al, 2020). This may be because low [Ca 2+ ] e causes dissociation of the paracellular junctions, increasing epithelial permeability (Bhat et al, 1993; Ma et al, 2000; O’Keefe et al, 1987).…”

“…This may be because low [Ca 2+ ] e causes dissociation of the paracellular junctions, increasing epithelial permeability (Bhat et al, 1993; Ma et al, 2000; O’Keefe et al, 1987). In some fishes and larval amphibians acutely exposed to low pH, elevated and reduced environmental Ca 2+ levels substantially reduced and increased rates of passive net Na + loss, respectively (Cummins, 1988; Freda et al, 1991; Gascon et al, 1987; Gonzalez and Dunson, 1989; Kumai et al, 2011; McDonald and Rogano, 1986; McDonald et al, 1983). Ca 2+ may act on the TJ directly, but also indirectly through Ca 2+ -dependent proteins in adherens junctions (AJ) which sit basally to the TJ (Brown and Davis, 2002).…”