Gastrointestinal transit times in mice and humans measured with 27Al and 19F nuclear magnetic resonance

Gastric emptying and gastrointestinal (GI) transit times in mice and humans were monitored noninvasively by using 27Al and 19F nuclear magnetic resonance (NMR). Al(3+) bound to ion-exchange resin and perfluorononane were administered orally as selective and specific markers for the stomach and the entire GI tract, respectively. 27Al- and 19F-MR spectroscopy (MRS) was employed to follow quantitatively boli of the mixed markers in awake, fed mice over a period of 48 hr. The selectivity of the markers was confirmed by whole-body 1H-, 27Al-, and 19F-MRI of anesthetized mice. Gastric emptying in humans was also monitored with 27Al-MRS of aluminum-loaded ion exchange resin. GI transit was assessed by 19F projection imaging of pharmaceutical capsules tagged with perfluorononane. Quantitative analysis of the MR data revealed that gastric emptying in humans proceeded linearly, whereas in mice an exponential decay was observed. This difference is explained by the respective feeding patterns of humans and mice. Humans usually achieve nearly complete gastric emptying before each meal. In contrast, very short delays between successive food intakes in small animals result in successive dilution of the stomach contents. For stomach emptying in mice the exponential decay constant was 74 min, whereas the half-time of the linear gastric emptying in humans was 30 min.