RELAXATION OF LOWER ESOPHAGEAL SPHINCTER AND STIMULATION OF GASTRIC-SECRETION AND DIURESIS BY ANTIASTHMATIC XANTHINES - ROLE OF ADENOSINE ANTAGONISM

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Abstract
The study was designed to obtain information on selected extrapulmonary effects of enprofylline, an adenosine nonblocking alkylxanthine that is .apprx. 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 i.v. producing .apprx. 2 .mu.g/ml plasma) were examined in 8 healthy volunteers. Enprofylline and theophylline decrease LESP (by 5.0 .+-. 2.6 mm Hg, mean .+-. SD, P < 0.001, and by 5.8 .+-. 2.7 mm Hg, P < 0.001, respectively), but only theophylline stimulated gastric secretion (volume P < 0.01 and acidity P < 0.01) and urine production (volume P < 0.01 and NaCl excretion P < 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 diruesis) but not LESP.