Temperature-induced changes in blood acid-base status in the alligator, Alligator mississipiensis.

Gas exchange and arterial blood acid-base status were measured in 13 conscious alligators, Alligator mississipiensis, at 15, 25, and 35 degrees C. Arterial pH decreased by 0.250 units (from 7.635 to 7.385) and arterial carbon dioxide partial pressure increased by 11.4 Torr (from 11.8 to 23.2) as body temperature increased from 15 to 35 degrees C. No statistically significant changes occurred in arterial bicarbonate concentration. When OH-/H+ and alpha-imidazole were compared at each temperature, more variability was observed in OH-/H+, which increased from 8.7 to 12.0 as temperature increased from 15 to 35 degrees C. alpha-Imidazole remained essentially constant (0.76 at 15 degrees C and 0.80 at 35 degrees C). Body temperature increase caused marked increases in minute ventilation (VE), oxygen consumption (VO2), and carbon dioxide production (VCO2). The relative changes in these parameters resulted in a decrease in both VE/VO2 and VE/VCO2. The data of the present study are consistent with the concept that poikilotherms regulate their alveolar ventilation with changes in body temperature in order to keep OH-/H+ or alpha-imidazole constant.