Acid-base status and electrolytes in red blood cells and plasma of turtles submerged at 3 degrees C.

Two groups of adult Chrysemys picta bellii were studied; control turtles were maintained at 24 degrees C with free access to air, and diving animals were continuously submerged for 8.5-9.5 wk in aerated water at 3 degrees C. Cold submergence elicited a substantial lactic acidosis (blood pH 7.70; plasma [lactate-] 42.5 meq/l H2O). This acid load was largely balanced by changes in plasma strong ions; [Cl-] decreased, and [Ca2+] and [Mg2+] increased. Phosphorus nuclear magnetic resonance showed a significant reduction in the transerythrocyte pH gradient of diving animals (control, delta pH 0.66-0.90; diving, 0.00-0.11). This relative alkalosis of submerged turtle red cells was related to changes in blood cell (RBC) volume and composition; mean corpuscular concentration of hemoglobin [( Hb]) and RBC H2O content measurements revealed a 39% increase in RBC volume. Cell volume change was effected by a proportionally greater influx of K+ than Cl-, providing ionic compensation for the lactic acidosis. The obligatory H2O influx, which decreased the effective concentration of protein anion, and a 77% reduction of RBC [ATP] further contributed to the relative alkalosis. The combined effects of RBC alkalization and reduced [ATP] account for the observed Hb-O2 binding properties previously reported for submerged turtles at 3 degrees C (15).