Validation of Octanoate Breath Test for Measuring Gastric Emptying in Rats

BACKGROUND/AIMS: Lack of simple and repeatable tests hampers gastric emptying studies in rats. The aim of this study was to adapt the (14)C-octanoate solid gastric emptying breath test for application in rats, and to validate it against radioscintigraphic method. METHODS: After ingestion of a meal containing 3 mCi (99m)Tc and 2 µCi (14)C-octanoate, 23 male Wistar rats were placed on a gamma camera in a airflow container. Scintigraphic images were taken at regular intervals. The amount of (14)CO2 in a regularly replaced hyamine hydroxide solution, capturing CO2 in the outflow air, was counted using liquid scintillation spectrometry. (99m)Tc gastric retention curves and (14)CO2-excretion curves were fitted to their respective data. Three rats underwent the same procedures after administration of atropine. RESULTS: Overall Tr10% (time at which 10% of the original amount of (99m)Tc remained in the stomach) was 355 ± 64 minutes; Te90% (time at which 90% of total amount of (14)CO2 was excreted) was 325 ± 106 minutes. Their correlation coefficient was 0.71, R-square 0.50 and P < 0.005. Tr1/2 (50% of original amount of (99m)Tc remained) was 124 ± 28 minutes; Te1/2 (50% of total amount of (14)CO2 excreted) 114 ± 32 minutes. Their correlation coefficient was 0.83 with R-square of 0.69 and P < 0.00005. In 12 immobilized animals correlation was even better: correlation coefficient 0.84; R-square 0.71 and P < 0.001 (Tr10% was 388 ± 117 minutes; Te90% 532 ± 219 minutes; Tr1/2 of 165 ± 54 minutes; Te1/2 of 175 ± 67 minutes). Atropine significantly lengthened all emptying times: 904 ± 307 and 1461 ± 684 minutes for Tr10% and Te90%, respectively; and 432 ± 117 minutes for Tr1/2 and 473 ± 190 minutes for Te1/2. CONCLUSIONS: We adapted and validated the (14)C-octanoate gastric emptying breath test for application in rats.