Response of transmural electrical parameters across in vitro everted sacs of hamster jejunum to variations in...

1. The response of the electrical potential difference, short circuit current, and resistance across everted sacs of hamster jejunum to variations in the mucosal solution gassing rate was investigated. 2. Contrary to previous reports by others, it was found that the potential difference responds to increases in mucosal solution gassing rate by increasing in magnitude during the first 20 min of incubation. 3. The increases in potential difference were parallelled by increases in short circuit current but not by changes in resistance. 4. Increases in mucosal solution gassing rate increased epithelial cell O2 availability and this effect was determined to be due to increased stirring by gas bubbles. From the data, it was deduced that the minimum thickness of the mucosally located functional unstirred layer is between 0.08 and 0.16 cm when less than the full magnitude of electrical activity is observed across the everted sac preparation. 5. Serosal N2 or O2 had little or no effect on electrical parameters under maximum mucosal oxygenating conditions but dramatically affected these parameters when less than maximum mucosal oxygenating conditions were used. 6. Qualitative variations in the magnitude of the short circuit current across this preparation with respect to Cl- dependence were demonstrated. These variations were dependent upon the level of O2 availability, being apparent at high levels of O2 and absent at low levels. 7. It is concluded that the thickness of mucosally located unstirred layers can determine the O2 availability to the mucosa of everted sacs of hamster jejunum and thereby influence the observable magnitude and pattern of ionic dependence of the short circuit current across this preparation.