Crucian carp heart performance during anoxia and acidosis

The crucian carp (Carassius carassius L.) exhibits the unique ability among vertebrates to maintain cardiac performance at normoxic levels during prolonged anoxia exposure. This thesis investigates the hypothesis that this phenomenon is possible because the heart likely never experiences an extracellular pH below 7.4 due to the fish’s exclusive trait of converting lactate and H ions to ethanol. Performance of isolated spontaneous beating heart preparations from crucian carp was measured during exposure to 100 min of anoxia at pH 7.8 and graded acidosis (between pH 7.8 and 7.0) under both normoxia and anoxia at 6.5C. As expected, the results revealed that anoxic performance of the crucian carp heart is severely affected by a fall in pH below the normal anoxic level of 7.4. This suggests that in nature, heart performance may not be able to meet the needs of the body if blood pH is not maintained above 7.4. Additionally, the ability for these isolated hearts to recover from 40 min anoxia exposure at different pH (7.8, 7.4 and 7.0) was investigated in both crucian carp and in anoxia-intolerant koi carp (Cyprinus carpio L.). The latter hearts appeared irreversibly damaged by anoxia exposure despite showing a similar anoxic depression of cardiac performance as crucian carp hearts. Thus, the crucian carp heart has apparently an innate ability to tolerate anoxia, which the koi-carp hearts lacks, an ability that most likely reflect that the crucian carp has evolved to tolerate long-term anoxia supported by ethanol production.