Regulation of cation transport pathways and glycolytic enzyme activity by alterations in red cell volume

In the presence of NH4Cl and hypotonic solutions, Rana balcanica red cells respond by increasing their volume. The stimulation of cellular volume by h ypotonicity is more rapid than that of NH4Cl, while the maximum value is le ss than that observed in the presence of NH4Cl. Depending on the cause of s welling, (net uptake of NH4Cl or decrease in external osmolality) cells sho w specific responses. The NH4Cl treatment causes a significant increase in intracellular Na+, from 5.14 +/- 0.78 to 29.84 +/- 0.47 mmoles l(-1) cell, while hypotonicity leads to a significant decrease of this cation, to 385 /- 0.25 mmoles l(-1) cell in relation to the control, after 30 min of incub ation of Rana balcanica erythrocytes. In addition, amiloride significantly reverses the NH4Cl effect with respect to intracellular Na+. Both treatment s cause a significant K+ loss in comparison with controls. Two glycolytic e nzymes glyceraldehyde phosphate dehydrogenase (GAPDH) and pyruvate kinase ( PK) of Rana balcanica haemolysate were found to respond to the NH4Cl effect by significantly decreasing their activity. Copyright (C) 1999 John Wiley & Sons, Ltd.