Prolonged diving and recovery in the freshwater turtle, Pseudemys scripta—I. Lung and blood gases, pH, lactate concentrations and “cation” gap

Abstract

1. 1. The pattern of changes in lung and blood gases, HCO − 3 and lactate concentrations, and “cation” gap was studied in the freshwater turtle ( Pseudemys scripta elegans) during a 6-hr diving period and a 15-hr post-diving recovery period at 24 ± 1 (SD)°C. 2. 2. Lung and plasma paO 2 tensions fell progressively during the first hour of diving, reaching values of essentially zero at this time. 3. 3. Lung gas and plasma paCO 2 rose progressively during 6hr of diving, reaching values in excess of 100 torr during the 6 hr of diving. 4. 4. In the post-diving period pO 2 and pCO 2 values return to normal values within 5 min. 5. 5. Restoration of pH during the post-diving is slow and at 1 hr pH a , is significantly less than control values which are not achieved until 15 hr of post-diving. 6. 6. The sum of (HCO − 3) a + (lactate) a rises progressively during the dive, resulting in a peak “cation” gap of 24 m-equiv/1 at 6 hr of diving suggesting that the fall in pH causes a reduction of negative charge on plasma proteins.