Epithelial cells in the small intestine are regularly
exposed to strong gastric acid. When luminal pH decreases,
the intestinal epithelium cells can directly detect and
modulate their cellular response through the proton sensors,
e.g., ASIC1a, OGR1, and transient receptor potential
vanilloid 4 (TRPV4) [10–14]. The pH of half (pH0.5) and
full activation of OGR1 are 7.4–7.2 and 6.8, respectively
[15, 16]. OGR1 is associated with Gq proteins and acts