The ¹³C‐octanoic acid breath test: validation of a new noninvasive method of measuring gastric emptying in rats

Abstract

Currently available rat models for measuring gastric emptying are hampered by the necessity to kill the animals at the end of each experiment, which makes repetitive testing impossible. We have developed and validated a noninvasive test model, adapted from the 13C-octanoic breath test in humans, for repetitive measurements of gastric emptying in rats. Male Wistar rats were trained on a fixed protocol to eat a piece of pancake doped with 1 microg 13C-octanoic acid after 12 h fasting, and to stay thereafter in cylindrical glass cages. Breath tests were performed by a fully automated system of computer-guided switching valves, which collected consecutive breath samples. All breath samples were analysed by gas chromatography and isotope mass spectrometry. The area under the curve (AUC) from the cumulative 13CO2 excretion from 0 to 6 h was determined by the trapezium method to calculate the gastric half-emptying times (t(1/2)). Inter-day variability was determined. The effect of subcutaneous or intraperitoneal injection of saline was studied. The test was further validated for pharmacological interventions by oral administration of cisapride and parenteral administration of atropine, to induce, respectively. acceleration and delay of gastric emptying. Mean gastric emptying times +/- SD of 24 rats were 119.3 +/- 28.2 min, 138.7 +/- 26.0 min, and 124.5 +/- 30.9 min on three different test days. The mean coefficient of variation of three repeated measurements in the same 24 rats was 17.5%. No significant differences were observed after subcutaneous or intraperitoneal injection of saline. In a second test series of eight rats, cisapride significantly accelerated gastric emptying (mean t(1/2) 112.7 +/- 33.1 min, P < 0.05), while atropine caused a significant delay (mean t(1/2) 205.9 +/- 24.9 min, P < 0.05) when compared to control test results (mean t(1/2) 140.7 +/- 16.7 min) in the same rats. We validated the 13C-octanoic breath test to study gastric emptying in rats. This test method obviates the necessity to kill laboratory animals and allows repetitive measurements of gastric emptying to study its physiology or pathophysiology as well as the effect of pharmacological agents.

Simple and Noninvasive Breath Test Using 13C-Acetic Acid to Evaluate Gastric Emptying in Conscious Rats and Its Validation by Metoclopramide

“…Wyse and colleagues used 13 C-octanoic acid breath tests in ponies (20) and dogs (21) to evaluate gastric emptying. For smaller experimental animals, Schoonjans and coworkers (6) reported the use of a breath test with 13 Coctanoic acid in rats placed in metabolic air-tight cages.…”

13C-Acetic Acid Is More Sensitive Than 13C-Octanoic Acid for Evaluating Gastric Emptying of Liquid Enteral Nutrient Formula by Breath Test in Conscious Rats

“…1-3) Thereafter breath tests using 13 C-labeled compounds have been used in laboratory animals for evaluating physiological function, such as gastric empying 4,5) or liver function. 6) Recently, the present authors reported simple and noninvasive breath test system for monitoring gastric emptying by using 13 C-labeled acetic acid in conscious rats.…”

“…By using this method, gastric emptying time can be indirectly measured by monitoring the 13 CO 2 concentration in the expired air after a 13 C-labeled substance, such as acetic acid or octanoic acid, was ingested and absorbed from the duodenum.1-3) Thereafter breath tests using 13 C-labeled compounds have been used in laboratory animals for evaluating physiological function, such as gastric empying 4,5) or liver function. 6) Recently, the present authors reported simple and noninvasive breath test system for monitoring gastric emptying by using 13 C-labeled acetic acid in conscious rats.…”

Gastrointestinal Dysfunction in Chronic Liver Disease

“…In vitro studies indicated that alcohol and its metabolite acetaldehyde can inhibit the expression of tight junction protein, resulting in increased permeability [83,86] Additionally, alcohol can impair microtubule cytoskeleton in intestinal epithelial cells by inducing nitric oxide overproduction and oxidation/ nitration of cytoskeletal proteins [87]. A recent study has demonstrated that the changes to tight junctions occur in liver cirrhosis of mixed aetiology [88], and are not limited to alcoholic liver disease. More importantly, the reduction in tight junction proteins appears to relate to the disease severity, and is more pronounced in decompensated patients as compared to compensated patients [3].…”