Ontogeny of fetal rabbit upper gastrointestinal motility

Background. The gastrointestinal (GI) tract performs the digestion, propulsion, and absorption of nutrients both pre- and postnatally, although little is known about the development of fetal motility. We evaluated the development of GI motility using a novel fetal rabbit model. Methods. Nine pregnant rabbits were obtained and three litters were studied at day 24 (n = 24), 27 (n = 29), and 30 (n = 24) of their 31-day gestation. Under ultrasound guidance fetal position was identified, a spinal needle was percutaneously inserted into each fetal stomach, and fluorescein, labeled with color-coded microspheres, was injected. Two hours later, fetuses were delivered and weighed, and the small intestine was harvested. The absolute length of fluorescein traveled was measured by ultraviolet light optical density and the percentage motility was calculated by dividing the absolute length of fluorescein traveled by the total small intestinal length. Results. All injected fetuses survived. The length of fluorescein traveled significantly increased from day 24 (8.1 +/- 2.1 cm) to day 27 (18.8 +/- 4.6 cm) and 30 (22.6 +/- 5.2 cm). The length of fluorescein traveled significantly correlated with body weight on day 27 and 30. Calculated percentage motility significantly increased from day 24 to 30. However, percentage motility showed no correlation with fetal weight. Conclusions. This study describes a novel rabbit model for the assessment of in vivo fetal GI motility. Motility matured during the last third of gestation when assessed by the absolute length of fluorescein travel and the percentage motility. These results confirm that late-gestation fetuses have developed sufficient motility to propel potential nutrients, drugs, or gene therapy vectors to the small intestinal absorptive surface area. (C) 2001 Academic Press.