Effect of starvation on lipoprotein lipase activity in the liver of developing rats

Liver lipoprotein lipase activity in neonatal (1- and 5-day-old) rats was 2-3-times than in the liver of adult rats. In mid-suckling (15-day-old) or weaned (30-day-old) animals, it was not significantly different from the low activity detected in adult rats. Starvation resulted in a 3-fold increase of lipoprotein lipase activity in the neonatal liver, but did not affect the activity in the liver of mid-suckling, weaned or adult rats. When isolated livers from both 1- and 5-day-old pups were perfused with heparin, a sharp peak of lipoprotein lipase activity appeared in the perfusate. In fed neonates, the peak area accounted for about 70% of the total (released + non-releasable) activity. In starved neonates, the proportion of heparin-releasable activity increased up to about 90%. These results indicate that neonatal rat liver lipoprotein lipase activity is markedly affected by changes in the nutritional status of the animal, and the effect is restricted to the vascular pool of the enzyme, as was reported in extrahepatic tissues from adult rats.