Cadmium inhibition of Ca2+ uptake in rainbow trout gills

Abstract

The effects of cadmium (Cd2+) on calcium (Ca2+) transport in the gills of rainbow trout (Salmo gairdneri) were studied. The gill epithelium of freshwater fish represents a model for a Ca2+-transporting tight epithelium. Unidirectional Ca2+ fluxes in the gills were estimated in an isolated saline-perfused head preparation. Ca2+ influx was not affected when up to 10 microM Cd were added to the ventilatory water at the start of flux determinations (in vitro exposure). However, after 16 h in vivo preexposure of the fish to 0.1 microM Cd in the water, a 79% inhibition of Ca2+ influx was observed. Ca2+ efflux was not affected when up to 10 microM Cd were added to the ventilatory water during the flux determination. Ca2+ efflux in fish preexposed to 0.1 microM Cd for 16 h was also not affected; a preexposure to 1 microM Cd, however, resulted in a 173% increase in Ca2+ efflux rates. Tracer retention in the gill tissue indicated that both Ca2+ and Cd2+ enter the gill epithelium via a lanthanum (La3+)-inhibitable pathway. It is concluded that Cd2+ readily enters the branchial epithelial cells, similarly as Ca2+ does via La3+-sensitive apical Ca2+ channels. The inhibitory action of Cd2+ on transepithelial Ca2+ influx seems to result from an inhibition of the basolateral Ca2+ transport, occurring after a critical intracellular Cd2+ concentration has been reached.

Interactions between copper and cadmium modify metal organ distribution in mature tilapia, Oreochromis mossambicus

“…Metal-metal interactions after single metal exposure were shown by Gill et al (1992) who reported an increased Cu concentration in the gills of eels after Cd exposure. Previous experiments with single metal exposed fish have shown effects of sublethal concentrations of Cu or Cd on the number and function of ion transporting cells in the gills (Baker, 1969;Verbost et al, 1987;Reid and McDonald, 1988;Pratap and Wendelaar Bonga, 1993;Pelgrom et al, 1995). Exposure to low Cd concentrations resulted in an unexpectedly high increase in metal concentration in the gills.…”

Oxidative stress biomarkers and aggressive behavior in fish exposed to aquatic cadmium contamination

“…Freshwater fish are especially vulnerable to cadmium toxicity (Sorensen, 1991). The effects of cadmium on fish biology include growth retardation (Lemaire & Lemaire, 1992), inhibition of calcium uptake in gills (Verbost et al, 1987), changes in normal metabolic patterns (Soengas et al, 1996;Almeida et al, 2001), and altered reproduction and egg quality (Lin et al, 2000). Fish promptly respond to cadmium and other contaminants with alterations in detoxification enzymes (Jimenez & Stegeman, 1990), and it is well known that these enzymatic responses are modulated by several factors, among them temperature, age, nutritional status (Jimenez & Stegeman, 1990), and oxygen availability (Wilhelm Filho, 1996).…”

Dietary Ca inhibits waterborne Cd uptake in Cd-exposed rainbow trout, Oncorhynchus mykiss

“…In addition to causing direct Ž physical damage to gills Gardner and Yevich, . 1970 , cadmium disrupts calcium balance leading Ž to acute toxicity Roch and Maly, 1979;Verbost . et al, 1987;Reid and McDonald, 1988 .…”

“…Cadmium irreversibly blocks calcium uptake at the basolateral membrane of gill ionocytes through non-( )2q Ž competitive inhibition of Ca -ATPase Verbost . et al, 1987Verbost . et al, , 1988Verbost .…”

“…The combined action of inhibition of apical calcium uptake and inhibition of Ca 2q -ATPase by Ž cadmium leads to acute hypocalcemia Roch and . Maly, 1979;Verbost et al, 1987Verbost et al, , 1989 Water hardness has an ameliorating effect against cadmium uptake and toxicity in rainbow Ž trout Calamari et al, 1980;Pagenkopf, 1983;Part et al, 1985;Pascoe et al, 1986;Hollis et al, . 1997Hollis et al, .…”