Zahorsky-Reeves, J. 2011. The choice of bedding substrate, route of blood collection, and method of glucose determination all affect fasting blood glucose levels in C57BL/6 mice. American Association for Laboratory Animal Science [AALAS] Meeting Official Program, 738 (Abstract #PS80).

This study compared 4 bedding substrates (corncob, paper, hardwood chip, and wire-bottomed cage inserts) and 2 routes of blood collection (lateral tail vein and retroorbital sinus) in 6 male C57BL/6NCrl mice. Mice were maintained with ad libitum food and water on each bedding type for 1 wk, with at least 1 wk of rest on hardwood chip bedding in between sample collection. The night before blood sampling, the bedding was changed for fresh and food removed. Mice were anesthetized with isoflurane for all blood sampling. Blood was collected from both anatomic locations on each mouse up to 5 times over a course of 4 mo. Samples collected from the retroorbital sinus were analyzed both by glucometer and by chemistry analyzer machine following collection into serum separator tubes. The blood obtained from the tail vein was analyzed for glucose by hand-held glucometer only. Depending on the bedding provided, each mouse showed variability in the blood glucose values, even when the same bedding type was used at 2 different time points during the study. Significant differences in blood glucose were noted between the 2 collection routes on each testing day when analyzed by the hand-held glucometer. Variations in glucose levels were also observed when blood obtained from the retroorbital sinus was analyzed using the hand-held glucometer compared with the machine; these values were not significant across the group, but for some individual mice it approached a 20% difference or more at any one time point. These results stress the importance not only of consistency in the choice of bedding substrate for any experiment in which fasting glucose values may be important, but also indicating this information as well as the route of blood collection and method of analysis in any published material generated from such work.