N-nitrosoproline excretion in the presence and absence of gastric disease.

N-nitrosoproline (NPRO) excretion, an indicator of endogenous nitrosation, was measured in a group of hospital inpatients who were identified by endoscopy and gastric biopsy as either having gastric lesions or having healthy stomachs. NPRO was assayed in background 24-hour urine samples and samples collected after loading doses of nitrate and L-proline. The presence of gastric lesions was associated with altered gastric pH and concomitant changes in gastric juice nitrate and nitrite concentration. Gastric juice pH increased with increasing severity of gastric disease (P = 0.031) and patients with normal stomachs had a lower gastric pH than those with chronic atrophic gastritis (CAG) (3.0 vs. 6.5, P = 0.017). The changes in gastric juice nitrate concentration were in the reverse direction (P = 0.002 for trend) with normal patients having higher mean levels than CAG patients (12.7 vs. 5.5 micrograms/ml, P less than 0.0001). Nitrite concentration increased with severity of gastric disease but the results were not significant (normal, 82.9 vs. CAG, 223.4 ng/ml, P = 0.069). No association was found between the presence of gastric lesions and increased urinary NPRO excretion. Mutagenic activity was not detected in any of the gastric juice samples.