Oesophageal acidification does not increase lower oesophageal sphincter pressure

We studied the effect of distal oesophageal acidification on lower oesophageal sphincter (LOS) pressure in normal human volunteers and in cats. The distal oesophagus was acidified by intraluminal injection of 0.1N HCl (pH 1.2). The LOS pressure was recorded by a sleeve device while pharyngeal and oesophageal pressures were monitored by nonperfused, water filled catheters. In normal human subjects, distal oesophageal acidification did not elicit a change in LOS pressure. In anaesthetised cats, injection of acid into the distal oesophagus elicited immediate LOS relaxation followed by a secondary peristaltic sequence. With propagation of the peristaltic sequence into the LOS, the LOS pressure abruptly increased 20-100 mmHg and gradually returned to the preinjection value over 15-180 s. In the one instance in which we were able to acidify the distal oesophagus without evoking secondary peristalsis, the LOS pressure did not change. Injection of saline into the distal oesophagus evoked a response in the LOS and oesophageal body that was indistinguishable from that seen with acid. We conclude that contrary to common belief, distal oesophageal acidification itself does not affect LOS pressure in man or the cat.