Mitochondrial changes and carnitine status in fasting rats.

To elucidate mitochondrial morphology and related pathophysiology in the fasting state, liver mitochondrial area, plasma levels of carnitine and non-esterified fatty acids were measured in fed (N = 30) and fasted for 5 days (N = 28) rats. The rats were divided into three groups according to body weight: 100 g-group (aged 5 weeks), 200 g-group (aged 7-8 weeks), 400 g-group (aged 15-16 weeks). Electron microscopy of the liver revealed mitochondrial enlargement in fasted rats. There were significant differences in mitochondrial area measured by digitizer, between fasted groups with 100 g and 200 g body weights and the compatible fed groups. The grade of mitochondrial swelling was inversely proportional to the body weight (i.e. the age). The fasting induced decreased plasma levels of free carnitine and increased plasma levels of acylcarnitine. Plasma free carnitine levels in all fed rats appeared to be directly correlated to the body weight. The above mitochondrial swelling and abnormal carnitine status are hallmarks of Reye's syndrome (RS). These changes are not specific to RS but might be attributable to fasting.