Hepatic protein synthesis and secretion after jejunoileal bypass in the rat

The rat was used as an animal model to explore the mechanism responsible for the development of hepatomegaly and hypoproteinemia which commonly occur after jejunoileal bypass. Sprague-Dawley rats, 300 to 350 g, were divided into three groups of 12 animals. Six of the 12 rats per group served as study animals and six as controls. The first six were subjected to 90% jejunoileal bypass and the six controls were sham-operated and pair-fed. In the second group, six animals were subjected to 90% jejunoileal resection and six controls were sham-operated and pair-fed. Six animals in the third group were underfed so that their weights mimicked that of the bypassed animals and six controls were fed ad libitum. After 8 wk the animals were killed. Liver weights, hepatic protein content, and serum protein and triglycerides were determined. Synthesis and secretion of proteins and glycoproteins were measured using incorporation of ¹⁴C-leucine and ¹⁴C-glucosamine respectively, into hepatic and medium proteins by liver slices. Bypassed animals demonstrated hepatomegaly, decreased serum proteins and triglycerides, and increased hepatic protein content. While both protein and glycoprotein synthesis remained normal, the secretion of these proteins into the medium appeared to be impaired. Comparable changes did not occur after jejunoileal resection or after underfeeding. This study suggests that the impairment of glycoprotein and protein secretion may be a contributing factor in the increased liver weight and protein content in conjunction with decreased serum protein observed in the bypassed rat.