EVALUATION OF SOLID-PHASE LABELS FOR GASTRIC-EMPTYING STUDIES IN CATS

Development of appropriate radiolabeled diets for solid-phase gastric emptying studies in experimental animals is important for testing the effects of disease, drugs, surgical procedures and stress. This study evaluates the in vitro and in vivo stability of various radiolabels in commercially available dry, extruded and canned cat foods. Methods: D ry, extruded cat food was labeled with Tc-99m-pertechnetate, Tc-99m-su lfur colloid or Tc-99m-disofenin. Canned cat food was labeled with Tc- 99m-Dowex resin beads, Tc-99m-pertechnetate, Tc-99m-sulfur colloid or Tc-99m-disofenin. A sample of each labeled diet and Tc-99m-sulfur coll oid-labeled egg was digested in water, gastric juice, intestinal juice or gastric juice followed by intestinal juice, The samples were centr ifuged and the activity in the samples counted before and after remova l of the supernatant. Based on in vitro results, three labeled diets w ere fed to 10-12 cats for in vivo testing. Results: Tc-99m-Dowex beads had the best labeling efficiency in vitro, but were not stable in viv o, resulting in unacceptable levels of circulating Tc-99m. Technetium- 99m-disofenin labeling resulted in in vitro percent solid-phase retent ion of 92.5% and 89.5% in water and gastric juice, respectively, for d ry food and 86% and 94.9% in water and gastric juice, respectively, fo r canned food, Conclusion: Technetium-99m-disofenin is a suitable labe l for solid-phase gastric emptying studies using commercially availabl e cat foods.