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  • Title: Cadmium inhibition of Ca2+ uptake in rainbow trout gills.
    Author: Verbost PM, Flik G, Lock RA, Wendelaar Bonga SE.
    Journal: Am J Physiol; 1987 Aug; 253(2 Pt 2):R216-21. PubMed ID: 3618821.
    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.
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