On the Instability of K+ Influx in Erythrocytes of the Rainbow Trout, Salmo Gairdneri, and the Role of Catecholamine Hormones in Maintaining In Vivo Influx Activity

Abstract

The rate of K⁺ influx in washed trout erythrocytes was not stable and declined by 60 % over a 6 h period, but decreased only slowly thereafter. During this initial period the cells shrank, although [K⁺]₁ was maintained constant. Both ouabain-sensitive and furosemide-sensitive K⁺ influx were reduced by approximately equal amounts. Extensive modification of the saline composition produced no diminution of the loss of K⁺ influx activity, making it unlikely that the response was due to deficiencies in saline composition. The rate of K⁺ influx in unwashed cells was affected only slightly by noradrenaline and adrenaline. By contrast, K⁺ influx in cells which had been washed and incubated overnight before assay was stimulated 100–250% by these hormones. Half-maximal stimulation was at 2× 10⁻⁶ and 8 × 10⁻⁶ M respectively. Replacement of plasma by a saline containing 5 × 10⁻⁶ M adrenaline and noradrenaline resulted in high and stable K⁺ influx rates over a 6 h period. These results support the hypothesis that K⁺ influx in erythrocytes of freshly drawn blood is high as a result of stimulation by catecholamine hormones. Removal of the normal hormonal milieu, by washing of the cells, results in the rapid loss of K⁺ influx activity.