Relaxation of lower esophageal sphincter and stimulation of gastric secretion and diuresis by antiasthmatic xanthines. Role of adenosine antagonism.

The study was designed to obtain information on selected extrapulmonary effects of enprofylline, an adenosine-non-blocking alkylxanthine that is about 5 times more potent as a bronchodilator than the adenosine receptor antagonist theophylline. Effects of theophylline (5.0 mg/kg) on lower esophageal sphincter pressure (LESP), gastric secretion, and diuresis and of enprofylline (1.5 mg/kg intravenously producing about 2 micrograms/ml plasma) were examined in 8 healthy volunteers. Enprofylline and theophylline decreased LESP (by 5.0 +/- 2.6 mm Hg, mean +/- SD, p less than 0.001, and by 5.8 +/- 2.7 mmHg, p less than 0.001, respectively), but only theophylline stimulated gastric secretion (volume p less than 0.01 and acidity p less than 0.01) and urine production (volume p less than 0.01 and sodium chloride excretion p less than 0.01). Neither xanthine affected plasma gastrin. Enprofylline and theophylline can be expected to have a similar ability to reduce the barrier to gastroesophageal reflux, but only the latter would have additional stimulant effects on gastric secretion and diuresis. These findings may have clinical significance and suggest a role for adenosine in regulating gastric secretion (and diuresis) but not LESP.