Seasonal adaptation of crucian carp (Carassius carassius L.) heart: glycogen stores and lactate dehydrogenase activity

The glycogen content of the crucian carp heart followed a clear annual cycle, while the size of the heart remained constant throughout the year. Glycogen stores were very abundant at the beginning of the winter (8% of heart mass) and were consumed during the winter and spring, so the stores were at their minimum in early summer (1.4% in May). New glycogen depositions accumulated in the heart during summer and autumn, the maximum glycogen content being attained at the end of October. Glycogen occurred in two distinct granular forms: small β particles about 25 nm in diameter and large α particles about 100 nm in diameter. In late autumn glycogen was mainly in the form of small β particles, which were gathered in vast "glycogen seas" up to 45 μm in length and 10 μm in width. In spring and especially in summer the larger α particles were more numerous than β particles. Lactate dehydrogenase (LDH) activity of the crucian carp heart was relatively high and constant throughout the year. The kinetic properties of...