Enzymatic adaptations to asphyxia in the harbor seal and dog.
The activities of the glycolytic enzymes were determined in heart, liver, kidney cortex and cerebrum from the harbor seal (Phoca vitulina ) and the adult and newborn dog. Activities were similar in the four dog tissues as well as myocardium and brain tissue from both the newborn dog and seal. Most of the enzyme activities were markedly lower in kidney cortex and liver of the seal and the newborn dog, suggesting that the organs which are rendered ischemic in the diving seal or asphyxiated newborn dog have a lowered demand for glycolytic metabolism. This is perceived as an adaptation to prolong the time tissues can rely on anaerobic metabolism. Expression of the enzyme data in a 'similarity criterion' by dividing activity from an organ likely to be perfused during long diving or asphyxia (e.g., heart), by that from one rendered ischemic (e.g., kidney), yields a quotient which provides a convenient indicator of anaerobic potential. Such a treatment would reflect the contribution of a discrete tissue to the total anaerobic demand of the whole animal. The values thus generated for the glycolytic enzymes are generally higher in the seal and the newborn dog than in the adult dog, and suggest an index for determining the capacity of an animal to withstand repeated and variable asphyxia.