Segregation of gastric Na and Cl transport: a vibrating probe and microelectrode study

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Abstract
The short-circuit current (Isc) of resting Necturus gastric mucosa (approximately 20 microA/cm2) can be attributed to the algebraic sum of the net Cl- secretion and amiloride-inhibitable net Na+ absorption. We have attempted to identify the cell types [surface epithelial cells (SCs) or oxyntic cells (OCs)] responsible for the transport of these ions in Necturus gastric mucosa using microelectrodes (ME) and a vibrating probe (VP). Mucosae were mounted horizontally in an open-topped Plexiglas chamber either serosal side up for basolateral ME impalements of OCs or mucosal side up for apical impalements of SCs and VP measurements. Cell impalements were made under open-circuit conditions, and VP measurements were performed under short-circuit conditions. Impalements of OCs indicate that neither the ratio of their apical to basolateral cell membrane resistances (Ra/Rb = 1.3 +/- 0.2) nor their cell membrane potentials were affected by 10(-6) M mucosal amiloride. In contrast, impalements of SCs indicate that amiloride increased their Ra/Rb from 3.5 +/- 0.2 to 15.6 +/- 1.8 and hyperpolarized both cell membrane potentials by greater than 20 mV. VP measurements showed that the amiloride-induced change in the current from SCs (5.6 microA/cm2) accounted for the amiloride-induced change in the Isc (5.5 microA/cm2). A non-zero current (4.4 +/- 1.0 microA/cm2) measured over SCs in the presence of amiloride was due to contamination from current arising from the gastric crypts that contain the OCs.(ABSTRACT TRUNCATED AT 250 WORDS)