Long-term starvation in cave salamander effects on liver ultrastructure and energy reserve mobilization

The morphological alterations of hepatocytes of cave-dwelling salamander Proteus anguinus anguinus after food deprivation periods of one and 18 months were investigated and the concentrations of glycogen, lipids, and proteins in the liver were determined. Quantitative analyses of the hepatocyte size, the lipid droplets, the number of mitochondria, and volume densities of M and P in the hepatocytes were completed. After one month of food deprivation, the cytological changes in the hepatocytes are mainly related to the distribution and amount of glycogen, which was dispersed in the cytoplasm and failed to form clumps typical of normal liver tissue. After 18 months of food deprivation hepatocytes were reduced in size, lipid droplets were less numerous, peroxisomes formed clusters with small, spherical mitochondria, and specific mitochondria increased in size and lost cristae. Lysosomes, autophagic vacuoles, and clear vacuoles were numerous. The liver integrity was apparently maintained, no significant loss of cytoplasmic constituents have been observed. Biochemical analysis revealed the utilization of stored metabolic reserves in the liver during food deprivation. Glycogen is rapidly utilized at the beginning of the starvation period, whereas lipids and proteins are utilized subsequently, during prolonged food deprivation. In the Proteus liver carbohydrates are maintained in appreciable amounts and this constitutes a very important energy depot, invaluable in the subterranean environment.