Blood gas changes during panting in a small East African antelope, the dik-dik

Abstract

Five adult male dik-dik (Madoqua kirkii) were exposed in a climatic chamber to an air temperature of 45 degrees C. Measurements were made of rectal temperature (Tre) and respiratory frequency (f) and arterial blood samples taken before and during heat exposure were analyzed for pH, PCO2 and PO2. During exposure, Tre and f increased in all animals. In the first 80 min dik-dik displayed thermal tachypnea and minor changes in blood gases. Continued exposure lead to hyperpnea accompanied by a fall in PaCO2 and a rise in pH. PaCO2 at first fell and then increased toward or above control levels. The dik-dik did not display second phase breathing. This observation confirms that second phase breathing is not essential to the development of respiratory alkalosis. The main conclusion of the study is that the dik-dik, unlike another heat-adapted antelope, the wildebeest (Taylor, Robertshaw, and Hoffmann. Am. J. Physiol. 217:907-910, 1969), is unable to resist alkalosis during heat stress.