Gastrointestinal Intraluminal pH of Non-Fasted Mice (Mus musculus) of Various Strains and Vendors Including Germ-Free and Streptomycin-Treated Mice.

Mice are a valuable tool for preclinical research, enabling the investigation of fundamental questions about disease mechanisms, drug delivery, and pharmacokinetics. Intestinal pH influences drug delivery and pharmacokinetics of orally administered compounds. However, little is known about variations in pH along different sections of the mouse gastrointestinal tract. We therefore compared pH in 7 gastrointestinal tract sections of 48 male and female BALB/c, C57BL/6, and NMRI mice from 2 different vendors, as well as 8 streptomycin-treated and 8 germ-free BALB/c male and female mice from one vendor. The pH in the duodenum and cecum varied between strains and vendors. Relative to untreated barrier-bred mice, streptomycin-treated mice had significantly higher pH in the jejunum, and germ-free mice had significantly higher pH in the jejunum, cecum, and proximal colon, underlining the role of gut microbes in regulating pH levels throughout the gastrointestinal tract. In conclusion, we show that mouse strain, vendor, and microbial presence, but not sex, influence gastrointestinal pH in mice. Given the importance of gastrointestinal pH for pharmacokinetics, drug delivery systems, and gastrointestinal microbial behavior, these data will provide an important foundation for the choice of mouse models for research involving the gastrointestinal tract.