Responses of the competent and incompetent lower oesophageal sphincter to pentagastrin and abdominal compression.

Responses of the lower oesophageal sphincter (LOS) to pentagastrin, given by continuous intravenous infusion in doses ranging between 0 and 9 mug/kg/h, and to external abdominal compression were measured by infused catheters in healthy subjects and in a group of patients with reflux oesophagitis. In separate experiments, pressures were measured both by sensors stationary within the LOS, and by repeated continuous withdrawals of sensors from stomach to distal oesophagus. In normal subjects, doses of pentagastrin within the physiological range (0.9 mug/kg/h) produced modest but statistically significant increases in LOS pressure. By comparison, sphincteric responses in patients with oesophagitis were small and a dose of 4-5 mug/kg/h was the lowest that produced a significant increase in LOS pressure. During abdominal compression increases in LOS pressure did not significantly exceed increases in intragastric pressure in either patients or normal subjects. This was so at all doses of pentagastrin that were tested. Hence, there was no evidence of synergism between the effects of pentagastrin and abdominal compression upon the LOS. We infer from our findings that gastrin does play a modest role in the physiological regulation of human LOS tone. Relative insensitivity of the incompetent LOS to pentagastrin represents, we believe, sphincteric muscle failure. Our results are not consistent with the hypothesis that LOS incompetence is due to loss or impairment of an adaptive response of the LOS to alterations in intra-abdominal pressure.