Validation of octanoate breath test for measuring gastric emptying in rats

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.

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.

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.

We adapted and validated the (14)C-octanoate gastric emptying breath test for application in rats.