Influence of Secretin and Pentagastrin on the Circadian Rhythm of Cell Proliferation in the Intestinal Mucosa in Rats

Abstract

The effects of Secretin (3.5 U/100 g) and Pentagastrin (25 μg/l00 g) on cell renewal in jejunal mucosa was studied in male Wistar rats. The labeling index (LI), mitotic index (MI), and histogram of the distribution of labeled cells were measured at 4-hour intervals during 24 h after intraperitoneal injection of hormones and compared with results obtained in control animals. DNA label was obtained by injection of tritiated thymidine (70 μCi/100 g) 30 min before sacrificing the animals. The proliferation of intestinal cells in rats was marked by a circadian rhythm with a nocturnal peak of DNA synthesis. After Pentagastrin, the LI remained high for 16,20, and 24 h after injection, during the time the control levels diminished in the circadian rhythm. The normal MI and the enlargement of the zone of proliferation support the hypothesis of a stimulating effect of gastrin on intestinal cell renewal. After Secretin, the LI peak of the cycle was suppressed and the MI decreased, indicating an inhibiting effect of Secretin on intestinal cell renewal. Secretin and gastrin act as trophic factors on intestinal mucosa and produce opposite effects on cell proliferation.