Glycogen dynamics of crucian carp (Carassius carassius) in prolonged anoxia.

Abstract

Mobilization of glycogen stores was examined in the anoxic crucian carp (Carassius carassius Linnaeus). Winter-acclimatized fish were exposed to anoxia for 1, 3, or 6weeks at 2°C, and changes in the size of glycogen deposits were followed. After 1week of anoxia, a major part of the glycogen stores was mobilized in liver (79.5%) and heart (75.6%), and large decreases occurred in gill (46.7%) and muscle (45.1%). Brain was an exception in that its glycogen content remained unchanged. The amount of glycogen degraded during the first anoxic week was sufficient for the anaerobic ethanol production for more than 6weeks of anoxia. After 3 and 6weeks of anoxia, there was little further degradation of glycogen in other tissues except the brain where the stores were reduced by 30.1 and 49.9% after 3 and 6weeks of anoxia, respectively. One week of normoxic recovery following the 6-week anoxia was associated with a complete replenishment of the brain glycogen and partial recovery of liver, heart, and gill glycogen stores. Notably, the resynthesis of glycogen occurred at the expense of the existing energy reserves of the body in fasting fish. These findings indicate that in crucian carp, glycogen stores are quickly mobilized after the onset of anoxia, with the exception of the brain whose glycogen stores may be saved for putative emergency situations.