EFFECTS OF SEROSAL-SIDE ACIDOSIS ON CELL PH (PH(I)) AND MEMBRANE ELECTRICAL-PROPERTIES IN GASTRIC-MUCOSA

Acute gastric mucosal injury and bleeding occur in the settings of bot h respiratory acidosis or metabolic acidosis secondary to systemic sep sis or shock, Respiratory acidosis, however, is more predictably assoc iated with acute injury than metabolic acidosis, We hypothesized that the gastric surface epithelial cells are more susceptible to acute inc reases in PCO2 than to acute decreases in HCO3-, even for the same lev el of extracellular acidification, To evaluate this hypothesis, we use d intracellular microelectrodes to measure pH(i), cell membrane potent ial (V-c), as well as ion conductances of the apical (G(a)) and basola teral (G(b)) membranes and the paracellular pathway (G(s)) in gastric mucosal cells during acute changes in serosal PCO2 or HCO3-, Necturus antral mucosae were mounted in Ussing chambers, perfused on both sides by Ringer solution (40 mmHg PCO2, 18 mM HCO3-, pH 7.3), Measurements were performed before and during increases in PCO2 (80 mmHg, pH 7.0) o r decreases in HCO3- (7.2 mM, pH 6.8 or 2.4 mM, pH 6.4), Both forms of acidosis acidified pH(i), depolarized membrane potentials, and decrea sed ion conductances across apical and basolateral membranes, but not the paracellular pathways, For the same level of extracellular acidifi cation, increases in PCO2 were more effective than acute decreases in HCO3- in acidifying pH(i) and eliciting disturbances in voltage-genera ting and ion permeability properties of the cell membranes, These find ings suggest that pH-buffering mechanisms in gastric surface cells res pond less effectively to high PCO2 than low HCO3. (C) 1996 Academic Pr ess, Inc.