Intestinal surface acid microclimate in vitro and in vivo in the rat.

The presence of the intestinal surface acid microclimate (ISAM) has long been suggested. Controversy, however, still exists as to the existence, general characteristics, and requirements of this microclimate. We examined the existence and distribution of the ISAM along the rat small intestine and colon and determined its general characteristics. The results clearly demonstrate the existence of the ISAM in vitro and in vivo. Glucose and sodium in the incubation medium, as well as normal intracellular metabolism, are essential requirements for the formation and maintenance of the ISAM. We conclude that the ISAM is a normal physiologic phenomenon of the luminal surface of the intestine.