Role of Taurine in Cellular Volume Regulation in Erythrocytes of Air-Breathing Catfish (Clarias magur) Under Osmotic Stress

The present study investigated the role of taurine in cellular volume regulation of erythrocytes isolated from freshwater air-breathing magur catfish (Clarias magur) under osmotic stress. Exposure of erythrocytes, pre-loaded with or without taurine, to hypotonic medium (− 80 mOsmol/L) led to a significant decrease in taurine level in the erythrocytes due to efflux of taurine through a band 3 transporter protein present in the plasma membrane with a slight increase in cellular volume of erythrocytes by 12–13%, whereas incubation of erythrocytes with hypertonic medium (+ 80 mOsmol/L) with taurine caused a significant uptake of taurine by the erythrocytes through the Na⁺-dependent pathway but without any loss of taurine from the erythrocytes which was accompanied by a slight decrease in the cellular volume of erythrocytes by 11–12%. Furthermore, a direct correlation between the osmosensitive cellular volume and taurine release could be established in the erythrocytes of magur catfish under hypotonic stress (r = 0.9921). In conclusion, the erythrocytes of air-breathing magur catfish do possess a very efficient taurine-dependent volume regulatory mechanism to resist the changes in cellular volume under anisotonic conditions as a unique adaptational strategy to defend against the osmosensitive changes in cellular volume of erythrocytes.