Reovirus Type 3 Infection in a Suckling Mouse: the Effects on Pancreatic Structure and Enzyme Content

Summary: Alterations in pancreatic function and structure were examined in suckling mice infected intraperitoneally with reovirus type 3. The results were compared to pancreatic zymogen enzyme activities and histology in adult mice infected with the same virus. No effect of the reovirus type 3 on the adult mice could be elicited. In contrast, the suckling mice infected by the reovirus type 3 revealed a definite change in pancreatic zymogen enzymes. However, the zymogen enzymes were affected in a nonparallel fashion and three groups of enzymes with different responses were noted. Amylase and lipase activities were significantly diminished (P < 0.001) at 6 days of viral infection. The endopeptidases, trypsin (P < 0.025) and chymotrypsin (P < 0.001) activities were increased significantly in the infected group. The exopeptidases, carboxypeptidase A and B in the infected animals were not changed significantly compared to the control. It seems reasonable that the reovirus type 3 infection in the suckling mouse causes diminished lipase and amylase activities that might contribute to the pathogenesis of viral enteritis. Speculation: Studies on viral enteritis in infants and young animals have primarily implicated changes in the small intestine as the cause of diarrhea. The viral invasion of the intestinal mucosa causes villous cell destruction and as a consequence, the mucosa generated is immature and incapable of handling normal salt and water absorption. In addition, changes in pancreatic function as a result of an extension of the viral infection to the pancreatic parenchyma might contribute to the pathophysiologic mechanisms operating in viral enteritis. In the infected suckling mice, only amylase and lipase activities are diminished to a large extent, while trypsin and chymotrypsin activities are elevated and carboxypeptidase A and B activities remain unaffected. The nonparallel change in pancreatic enzymes toward a viral insult can be explained by a separate effect of the virus on the biosynthesis of each of the zymogen pancreatic enzymes. It is conceivable that amylase and lipase while in a developing stage, are more affected by the virus than the other pancreatic enzymes which are already developed to a certain extent. Another explanation is that lipase and amylase activities are intrinsically more prone to be decreased in response to different disease states affecting the pancreas. Diminished lipolytic and amylolytic activities due to viral gastroenteritis is a possible contributing factor of the diarrhea in infants and children.