title: Membrane potentials and chloride activities in epithelial cells of Aplysia intestine.
abstract: Microelectrodes were used to measure the potential difference across the mucosal membrane (psi m) of cells lining the mucosa of isolated Aplysia californica intestine. In glucose-free sodium chloride seawater medium psi m was -68.2 +/- 2.2 mV, the cell interior negative relative to the mucosal bathing medium. Simultaneously, the transmural potential difference (psi m leads to s) was recorded and its value averaged -0.4 +/- 0.1 mV (serosa negative). The addition of D-glucose to the mucosal compartment depolarized psi m to -62.1 +/0 2.5 mV and hyperpolarized psi m leads to s to -1.5 +/- 9.1 mV. Intracellular chloride activity (aCli) was also determined in Aplysia intestinal cells using single-barreled ion-exchange microelectrodes. In the absence of D-glucose the mean aCli was 10.1 +/- 0.5 mM, whereas after mucosal glucose addition the paired mean aCli increased significantly to 14.2 +/- 0.6 mM. Both aCli values were less than those predicted by the electrochemical equilibrium for chloride across the mucosal membrane. An active chloride transport mechanism located in the lateral-serosal membrane of the surface epithelial cells is proposed to explain these observations.
mesh_terms: D000818:Animals; D001048:Aplysia / Q000502:physiology*; D001693:Biological Transport, Active; D002712:Chlorides / Q000502:physiology*; D005947:Glucose / Q000378:metabolism; D007408:Intestinal Absorption; D007413:Intestinal Mucosa / Q000502:physiology; D008564:Membrane Potentials; D012621:Seasons
chemical_list: D002712:Chlorides; D005947:Glucose