Effects of hypoxic adaptation on myocardial performance and metabolism of Zoarces viviparous

Abstract

Zoarces viviparous were maintained in either normoxic or hypoxic ([Formula: see text], 4–4.7 kPa) water for 4–6 weeks. The hypothesis that adaptation to hypoxia results in an increase in the potential for anaerobic energy production in heart was tested. There was no difference in the activities of key enzymes of energy metabolism or in the content of myoglobin between the hearts from control or experimental fish. However, ventricular strips from animals adapted to hypoxic conditions were better able to sustain tension development than hearts from control animals during anoxia in the presence of high levels of external Ca2+. A combination of high Ca2+ and glucose was particularly effective in improving performance. The data suggest that hypoxic adaptation leads to an enhancement of Ca2+-activated carbohydrate mobilization but that the enzyme complement required to process the additional glycolytic flux is already in place.