INSULIN AND INTESTINAL EPITHELIAL-CELL PROLIFERATION

The effects of modification of the levels of endogenous plasma insulin on intestinal epithelia cell proliferation were investigated in rats maintained by total parenteral nutrition (TPN) using either a TPN diet that was high in glucose, or a low glucose (hypocaloric) TPN diet and in orally fed rats (normal and sham operated). The rats were put on t heir respective treatments for 7 days and were then injected with vinc ristine sulphate to arrest cells as they entered metaphase. Intestinal tissue was fixed for the determination of crypt cell production rate (CCPR) and blood plasma was taken for hormone radioimmunoassay. Sham o peration had no effect on either plasma hormone levels or on CCPR. The standard TPN diet was associated with significantly reduced levels of gastrin, peptide YY and enteroglucagon. Gastrin and PYY were further reduced by the hypocaloric diet. However, plasma insulin was much incr eased in the TPN but not in the hypocaloric group. Small intestinal CC PR was reduced in the TPN groups, but no difference was observed betwe en the standard and the low calorie TPN diets. The lack of difference in CCPR between the two TPN diets despite the massive elevation of pla sma insulin strongly suggests that insulin does not have a substantial role in the control of gastrointestinal epithelial cell renewal.