Quantitative Ultrastructural Studies of Hepatocytes from Fed and Starved Frogs

Stereological analysis of liver tissue excised from mature female Rana pipiens starved for 59 days and from a fed control group was conducted both a t the light and electron microscopy levels. Average cellular volume decreased by more than a factor of 4 following prolonged fasting. Nuclear volume was not significantly decreased. Mitochondria1 volume per cell showed a slight, though not statistically significant, decrease from 540 p m 3 to 420 pm3. Rough endoplasmic reticulum decreased in absolute surface area per cell from 13,600 pm2/cell to 3,000 pm2/cell after starvation, but its surface density in the cytoplasm remained relatively constant. Lipid decreased from 650 p m 3 per cell to less than 1 pm3 per cell after fasting. Glycogen decreased from 49% of hepatocyte cytoplasmic volume to less than 15%, a decrease in absolute volume from 4,000-240 p m 3 per cell. Glycogen changed from the a to the P-configuration during fasting. Condensed cross-banded fibers or sheets formed within the rough endoplasmic reticulum cisternae of some fasted animals. The significance of these results relative to the energy metabolism of poikilotherms