EFFECT OF DIETARY INSULIN ON THE RESPONSE OF SUCKLING MICE ENTEROCYTES TO ESCHERICHIA-COLI HEAT-STABLE ENTEROTOXIN

Effect of insulin on the response of suckling mice to the enterotoxige nic Escherichia coli heat-stable enterotoxin (STa) was studied. Four g roups (8-10 in each group) of 2-day-old Swiss Webster suckling mice we re used. For this study, 5, 10, 25 and 50 mu g of insulin was given or ally to half the mice in each group for 7 days. The rest of the mice i n each group were given normal saline as intra-litter controls. After 7 days, a suckling mouse assay in which 1 mu g of STa was given to all mice in insulin-treated and control groups was performed. Enterocyte suspensions were prepared from mice in all groups. Intestinal tissue s amples were taken for electron microscopy. Interaction of STa with its putative receptor on the enterocytes was evaluated using indirect imm unofluorescence and flow cytometry. The suckling mouse assay revealed a significant increase in the gut weight to body weight ratio in all m ice in the insulin-treated groups compared to control mice (P < 0.05). Flow cytometry and indirect immunofluorescence analyses suggested tha t insulin had an up-regulatory effect on the STa-receptor level. Simil arly, insulin was found to increase intestinal brush border membrane d ifferentiation as indicated by the increase in the inward movement of milk particles through the intestinal mucosa. Insulin seems to modify the structure-function of the brush border membrane including the resp onse of suckling mice to STa. This study may provide further insights into the mechanism of STa/receptor interaction, which is a major cause of diarrhea in newborn animals and human infants. (C) Inra/Elsevier, Paris.