CELL-SURVIVAL IN RABBIT GASTRIC GLANDS - EFFECT OF EXTRACELLULAR PH, OSMOLARITY, AND ANOXIA

Although backdiffusion of luminal acid is regarded as a common mechani sm of gastric injury, the extracellular pH (pH(o)) at which cells are irreversibly injured is not well defined. Exclusion of the fluorescent dye propidium iodide was used to estimate cell survival in rabbit gas tric glands incubated in buffers of pH. 8.0-2.0. Mean survival (+/- SE ) for n = 6 experiments at 2 h in a HEPES buffer of 300 mosM at pH. 8. 0, 7.0, 6.0, 4.0, and 2.0 was 80 +/- 3, 91 +/- 2, 90 +/- 2, 71 +/- 2, and 17 +/- 4%, respectively. Survival at acidic pH. was improved in a high KCl buffer: 78 +/- 3 and 38 +/- 7% at pH. 4.0 and 2.0, respective ly. Survival in HCO- buffers was 73 +/- 3, 88 +/- 2, and 92 +/- 3% at pH(o) 8.0, 7.4, and 6.0. Brief (5 min) exposure to pH(o) 4.0 followed by reexposure to pH(o) 7.4 had no effect on acid secretion as estimate d by [C-14]aminopyrine uptake or cellular viability over 4 h. The infl uence on cell survival of changes in pH. under conditions of chemical anoxia and in buffers of different osmolarity was investigated. Chemic al anoxia was induced using 2.5 mM KCN and 2.0 mM iodoacetic acid (IAA ) to inhibit oxidative phophorylation and anaerobic glycolysis. Surviv al in glands exposed to KCN and IAA in HEPES buffer was 54 +/- 5, 82 /- 3, and 87 +/- 2% at pH(o) 8.0, 7.0, and 6.0. At pH. 7.4, survival o f untreated glands in HEPES buffers of osmolarity of 25, 42, 300, 600, and 900 mosM was 65 +/- 6, 77 +/- 2, 87 +/- 1, 72 +/- 4, and 65 +/- 6 % (n = 6-11). Survival under conditions of chemical anoxia was not alt ered by changes in buffer osmolarity (42.6-600 mosM) or by the use of a high KCl buffer. We conclude that gastric glands are more tolerant t o acidic than alkaline pH(o) high-KCl solutions are protective under s everely acidic conditions, glands are very tolerant to changes in buff er osmolarity, mildly acidic pH. values (7.0-6.0) are protective under conditions of chemical anoxia, and glands tolerate brief exposure to very acidic pH. without loss of function or structural integrity.