Ultrastructure of the liver of reindeer calves under different nutritional conditions

A total of 12 reindeer calves were divided into two groups and the volume densities of liver cytoplasmic structures were counted using TEM. The six animals in group 1 were allowed to graze freely while those in group 2 were kept in pens and fed with lichens. All of them had a negative energy balance and lost weight from November to April, group 1 by 14.9% and group 2 by 24.8%. In spite of the weight losses, no significant changes in volume densities occurred during the winter. Glycogen remained fairly steady and there was no fatty infiltration into the hepatocytes. The very low incidence of Golgi apparatus in the hepatocytes may have been due to the inhibition of protein and lipid synthesis during the winter. These results point to substantial adaptation to extreme environmental conditions. The animals in group 1 apparently moved about more, which may have caused a greater breakdown of glycogen, resulting in turn in a lower volume density of glycogen in January and March.