ABSTRACT
Exposure of brown trout (Salmo trutta) in fresh water to 0.15 mmol l−1 external thiocyanate for 1 h resulted in a significant decrease in chlorine concentration in the branchial mitochondria-rich (MR) cells from 37 mmol l−1 to 22 mmol l−1 . The intracellular sodium concentration in these cells decreased by a similar amount, whilst the intracellular phosphorus concentration increased significantly. In contrast to the MR cells, 0.15 mmol l−1 external thiocyanate had no effect on the intracellular ion concentrations in the pavement epithelial cells. Thiocyanate is known to inhibit chloride uptake in a number of freshwater animals and therefore these data suggest that it is only the MR cells that are involved in the uptake of Cl− in brown trout.
