| The aim of these studies was to explore the lipid metabolism and liver development of neonatal pigs and the impacts of intrauterine growth retardation (IUGR). Fifteen normal weight (NW) and fifteen IUGR neonatal pigs were killed and sampled on newborn (day 0), day 3 and day 7 after birth, respectively. The activities of enzymes and some biochemical indices were analyzed according to appropriate methods. The results were demonstrated as follows:1 Lipid metabolism in normal neonatal pigsThe concentrations of plasma triglyceride (TG) and glucose in piglets were low at birth, and increased severely during the first 3 postnatal days (P<0.01 and P<0.0001, respectively), and maintained unchanged thereafter. In contrast, there was a marked decrease in the concentration of plasma free fatty acid (FFA) in the piglet right after birth (P<0.05). Liver TG content had no significant variation in the first week after birth. From birth to 7 days old, the concentrations of total cholesterol (TC), low density lipoprotein-cholesterol (LDL-C) and high density lipoprotein-cholesterol (HDL-C) all increased greatly in piglet plasma (P<0.01).In this experiment, both the activities of hepatic lipase (HL) and malate dehydrogenase (MDH) increased markedly during the first 3 postnatal days (P<0.05). From day 4 to day 7, the activity of HL showed a tendency to increase in plasma and to decrease in liver.The rapid increases of plasma fats in neonatal pigs suggest that fats become a major energy source for piglets in a short postnatal period. In addition, the results indicated that great changes took place in lipid metabolism in piglets during the early postnatal period.2 Developmental patterns and function of the liver in neonatal pigsThe hepatocyte cords were arranged in a radial mode in neonatal pig liver. There were abundant mature cellular organelles such as mitochondria and rough endoplasmic reticula in the liver of neonatal pigs. Liver weight increased at a higher rate than body weight in the first 7 days, especially in the first 3 days after birth. Similarly, liver protein content increased significantly in the first postnatal week (P<0.01). In contrast, liver glycogen content was highest at birth and decreased markedly after birth (P<0.01). DNA concentration was lowest (P<0.05) and RNA concentration highest (P<0.05) in the liver of 3-day old piglets.During the first week after birth, the activity of glutamic-pyruvic transaminase (GPT) increased greatly in plasma (P<0.0001), but tended to decrease in liver. The activity of glutamine-oxaloacetic transaminase (GOT) was highest on day 3 both in plasma and in liver.The activities of superoxide dismutase (SOD), CuZnSOD and MnSOD were highest in the liver of piglets at birth, and decreased gradually in the first postnatal week. The activity of glutathione peroxidase (GSH-Px) was lowest on day 3 (P<0.05). On the contrary, the activity of catalase (CAT) increased from newborn to day 3 (P<0.01) and maintained at a steady level between day 4 and day 7. In addition, all the contents of hydroxyl radical ("OH), lipid peroxide (LPO) and malondialdehyde (MDA) were found highest in the liver of newborn piglets.These results showed that the hepatocytes had already developed both in structure and in function. In addition, the abundant liver glycogen at birth played a critical role in maintaining the homeostasis of plasma glucose and energy metabolism in neonatal pigs. However, there were higher radical concentration and severe lipid peroxidation in the liver of piglet at birth. During the short period after birth, both the size and the weight of liver increased greatly, and the proportion of liver parenchyma increased to a certain degree in the piglet. In the meantime, great changes took place in the capabilities of antioxidation and amino acids metabolism in piglet liver.3 The impacts of IUGR on liver development and lipid metabolism in neonatal pigsWhereas liver glycogen content showed a tendency to be lowered in IUGR piglets, there were no significant differences in the... |
