Establishment of a Protocol for Determining Gastrointestinal Transit Time in Mice Using Barium and Radiopaque Markers

Objective: The purpose of this study was to establish a minimally invasive and reproducible protocol for estimating the gastrointestinal (GI) transit time in mice using barium and radiopaque markers. Materials and Methods: Twenty 5- to 6-week-old Balb/C female mice weighing 19-21 g were used. The animals were divided into three groups: two groups that received loperamide and a control group. The control group (n = 10) animals were administered physiological saline (1.5 mL/kg) orally. The loperamide group I (n = 10) and group II (n = 10) animals were administered 5 mg/kg and 10 mg/kg loperamide orally, respectively. Thirty minutes after receiving the saline or loperamide, the mice was administered 80 ${\mu}L$ of barium solution and six iron balls (0.5 mm) via the mouth and the upper esophagus by gavage, respectively. Afterwards, the mice were continuously monitored with fluoroscopic imaging in order to evaluate the swallowing of the barium solution and markers. Serial fluoroscopic images were obtained at 5- or 10-min intervals until all markers had been excreted from the anal canal. For analysis, the GI transit times were subdivided into intestinal transit times (ITTs) and colon transit times (CTTs). Results: The mean ITT was significantly longer in the loperamide groups than in the control group (p < 0.05). The mean ITT in loperamide group II (174.5 ${\pm}$ 32.3) was significantly longer than in loperamide group I (133.2 ${\pm}$ 24.2 minute) (p < 0.05). The mean CTT was significantly longer in loperamide group II than in the control group (p < 0.05). Also, no animal succumbed to death after the experimental procedure. Conclusion: The protocol for our study using radiopaque markers and barium is reproducible and minimally invasive in determining the GI transit time of the mouse model.