Direct measurement of mucosal surface pH of pig jejunum in vivo.

The mucosal surface pH of pig jejunum was measured in vivo. When the pH in the bulk phase of the perfusing buffer solution was 7.10, the pH at the mucosa (as measured by a miniaturised glass pH electrode) was 6.19 +/- 0.04 (n = 19). This relatively acidic mucosal surface pH is not an anoxic artefact since anoxia resulted in a significant alkalinisation of the mucosa. This finding, that the pig, like man and the rat, has a jejunal "acid microclimate" has important implications for weak electrolyte absorption from the upper small intestine of this species as well as for any other pH dependent brush border process.