Effect of luminal acidification on guinea pig gastric mucosa

H⁺ secretion was studied in guinea pig fundic mucosa incubated in (A) bicarbonate-Ringer's gassed with 95% O₂-5% CO₂, or (B) HEPES gassed with 100% O₂ before and after luminal pH was lowered to 2.0 for periods up to 90 min. At pH 2.0 for 60 min, H⁺ secretion in group A tissues fell by 35±4% (P=0.02) from a control rate of 1.35±0.09 eq/cm²/hr and in group B tissues by 50±11% (P=0.01) from a control rate of 1.59±0.08 eq/cm²/hr. After 90 min at pH 2.0, H⁺ secretion in group A fell by 53±8% (P=0.02) from a control rate of 1.47±0.07 eq/cm²/hr and in group B fell by 44±6% (P=0.01) from a control rate of 1.38±0.07 eq/cm²/hr. Histamine 1×10^–4 M stimulation following exposure to pH 2.0 for 90 min increased secretion in group A tissues from 0.80 ±0.14 to 1.06±0.13 eq/cm²/hr (P<0.05), compared with an increase in nonacidified controls from 1.15±0.22 to 1.80±0.20 eq/cm²/hr (P<0.05) and in group B tissues from 1.27±0.10 to 1.56±0.19 eq/cm²/hr (P<0.05) compared with nonacidified controls from 1.43±0.22 to 2.23±0.41 eq/cm²/hr (P<0.05). Secretory function and electrical characteristics were adversely affected by luminal acidification to pH 2.0 and suggested a breach in the mucosal barrier with damage to parietal cells.This study was funded by the National Institute of Health Grant No. AM 15681.