Disturbed small intestinal motility in the late rat pregnancy.

We investigated whether various periods of pregnancy might disturb rat gastrointestinal motility. When the proestrus of female rats occurred, they were housed with male rats. Motility studies were conducted on day 7 (first period), day 14 (second) and day 21 (third) of pregnancy, respectively. After the orogastric feeding of radiochromium marker, rats were sacrificed 15 min later. Gastric emptyings of pregnant rats measured at various periods did not differ from the nonpregnant diestrus controls. The geometric center represented intestinal transits in the first, second and third periods of pregnancy and controls were (mean+/-SEM) 4.54+/-0.25, 4.47+/-0.17, 3.61+/-0.27 and 4.98+/-0.13, respectively (p < 0.01) while their plasma progesterone levels were 15.6+/-2.6, 18+/-1.4, 7.1+/-0.5 and 8.6+/-0.4 ng/ml, respectively (p< 0.01). This shows that late pregnancy inhibits small intestinal transit, whereas gastric emptying remains unchanged. Altered progesterone during pregnancy is not a main mediator to disturb intestinal transit.