A Novel Method for Measurement Gastric Emptying Using Three-dimensional Micro Computed Tomography in Small Live Animal

Abstract

c 2019 The Korean Society of Neurogastroenterology and Motility J Neurogastroenterol Motil, Vol. 25 No. 1 January, 2019 www.jnmjournal.org TO THE EDITOR: Alteration of gastric emptying (GE) is one of important pathophysiology in functional gastrointestinal disorders such as functional dyspepsia and diabetic gastroparesis. Therefore, it is essential to measure GE in investigating the pathophysiology of disease or new drug efficacy in the translational animal experiment. In small animals such as mice or rat, phenol red recovery with photospectrometry from stomach has been used for liquid GE. For solid GE, measurement of remnant gastric food after spontaneous ingestion of normal rat chow has been used. However, these methods require the sacrifice of an experimental animal and obtain only one-time point GE value. Recently, it has been recommended to minimize the sacrifice of an animal in the basic experiment. The non-invasive C-octanoic acid breath test was recently applied to rats and it allows repetitive measurements of GE. However, it is not possible to measure gastric volume in a live animal. We recently demonstrated that gastric volume could be measured in the rat using three-dimensional (3D) micro-CT (PolarisG90, Nano Focus Ray, Iksan, Korea; Fig. 1). Based on the experience of the previous experiment, we thought it would be possible to measure GE with 3D micro-CT in rat without sacrifice. We performed a preliminary experiment on whether 3D microCT can measure GE change by drugs in Sprague-Dawley rat (210-310 g). Rats were divided into control, delayed GE (DGE, pre-treated with atropine), and enhanced GE (EGE, pre-treated with bethanechol) groups. After overnight fasting, distilled water, atropine (7.5 mg/kg), and bethanechol (1 mg/kg) was given by intraperitoneal injection in each group, respectively. After 20 minutes of injection, 3 mL of radiopaque semisolid food was fed into the stomach by gastric gavage under isoflurane anesthesia. Radiopaque semisolid food was a mixture of commercial food thickener containing carbohydrate (EG, 20 kcal/6 g; Goodseed company, Seoul, Korea) and radio-contrast dye (easySB, 30 g barium/100 mL; Taejoon pharm, Seoul, Korea). The calorie of final semi-solid food was 167 cal/mL. Immediately after gastric gavage, baseline CT (fed volume) was performed, and after 1 hour freely moving time, second CT (residual volume) was performed. Conventional CT image was converted to a 3D image, and the volume of radiopaque gastric food was measured (Fig. 2). GE rate was calculated as [(fed volume A Novel Method for Measurement Gastric Emptying Using Three-dimensional Micro Computed Tomography in Small Live Animal JNM J Neurogastroenterol Motil, Vol. 25 No. 1 January, 2019 pISSN: 2093-0879 eISSN: 2093-0887 https://doi.org/10.5056/jnm18207 Letter to the Editor Journal of Neurogastroenterology and Motility