Strontium‐calcium transport across the gill of rainbow trout, (Salmo gairdnerii)

Abstract This study was performed using radioactive isotopes of calcium and strontium as tracers in a perfused gill preparation. There were two levels in the uptake rates for strontium and calcium: a passive rate of 0.5 × 10−7 cm/sec, and 1.8 × 10−7 cm/sec, respectively, and a tenfold higher energy dependent rate of 5.1 × 10−7 cm/sec for strontium and 17 × 10−7 cm/sec for calcium. There was no evidence of discriminatory interaction between calcium and strontium at the passive levels of transport. Strontium was found to substitute for calcium at the active transport levels only if the calcium concentration of the environmental water was below approximately 0.1 mM Ca++/1. The rate of calcium and strontium loss from the gill was estimated as about 20 times faster than the influx rates. This caused the postulation that the net transfer of calcium ions across the gill could change, dependent upon the degree of saturation of the calcium‐binding sites within the fish.