Blood changes in Bufo cognatus following acute heat stress

1. Various blood constituents were measured in an attempt to identify the effects of exposure of Great Plains toads to the critical thermal maximum (CTmax) and determine the time course of the onset of and recovery from these effects. 2. Tests for generalized tissue damage including serum glutamic-oxalacetic and glutamic-pyruvic transaminases (SGOT, SGPT), total protein and blood urea nitrogen (BUN) were unaffected by acute thermal stress. 3. Hematocrit, erythrocyte number, mean cell volume and hemoglobin concentration were also unchanged. 4. Blood glucose, lactic acid and creatine phosphokinase (CPK) levels all increased significantly. 5. Blood pH, PO2 and [HCO3-] also increased with acute heat stress while PCO2 decreased. 6. Long-term exposure to temperatures near the CTmax may cause severe tissue damage. Acute thermal stress does not appear to cause damage other than the short-term, reversible effects of strong physical exercise.