Relationship between acid neutralization capacity of saliva and gastro-oesophageal reflux

Saliva is an important factor in neutralization of oesophageal acid exposure, clinically manifested as gastrooesophageal reflux (GOR). The aim of this study is to compare the composition and the "capacity in acid neutralization" (CAN) of saliva in controls and patients suffering of GOR. We compared the composition of saliva from 56 patients who had symptoms of GOR with that of saliva from 20 healthy control subjects. After a standardized 24-hour period of pH-monitoring, 39 patients had normal pH reflux scores (normal acid score: NAc-GOR) and 17 had abnormal pH reflux scores (pathological acid score: PAc-GOR). Then, following a 10-h fast, total saliva was collected during ten minutes in all patients and in the healthy control subjects. The composition of the saliva samples was analysed and the titration curve was determined on 200 microliters aliquots by successive addition of 5 microliters volumes of 0.1 N Hcl. The GOR patients had significantly lower salivary concentrations of Na+ and of both free and bound sialic acids and had higher salivary concentrations of inorganic phosphates than the controls. These disorders were more marked in PAc-GOR patients. Initial pH was 7.43 +/- 0.43 in controls, 7.35 +/- 0.45 in NAc-GOR patients, and 6.91 +/- 0.53 in PAc-GOR patients. In the beginning of the titration curve, PAc-GOR patients were significantly different from NAc-GOR patients and from controls. Saliva of both groups of patients presented significant differences in the acidic portion of the titrations curves, at high volumes of added HCl. These data show that the composition of saliva was modified in patients with GOR disease compared to that of normal subjects. A difference in titration curves was also observed with a higher acidic buffering capacity in these GOR patients. The modifications in saliva composition suggest a role for inorganic phosophates in the acid neutralization capacity observed in GOR, perhaps linked with a adaptation to chronic acid exposure.