Effect of gastric inhibitory polypeptide on lower esophageal sphincter pressure in cats

Abstract

The effect of gastric inhibitory polypeptide on lower esophageal sphincter pressure was studied in cats to determine whether the effect was similar to that of its structurally related hormones, secretin, glucagon, and vasoactive intestinal peptide. Five healthy cats without endoscopic evidence of esophagitis were manometrically evaluated for 75 min using triple lumen open-tipped constantly perfused catheters. Exogenous gastric inhibitory polypeptide, 0.2 μg per kg per min, alone significantly decreased (P < 0.05) basal sphincter pressure within 15 min of administration to a maximum lowering of sphincter pressure of −13.8 ± 3.8 mm Hg at 45 min. Maximum mean serum gastric inhibitory polypeptide concentration, 428 ± 47 pg per ml, occurred at 15 min. Exogenous gastric inhibitory polypeptide also decreased lower esophageal sphincter pressure at all time periods (P < 0.02) when given during a constant pentagastrin infusion, 0.5 μg per kg per hr. Endogenous gastric inhibitory polypeptide was released by intraduodenal 20% glucose bolus injection or constant perfusion. After bolus glucose administration, serum gastric inhibitory polypeptide concentrations increased from undetectable values to a mean peak concentration of 657 ± 78 pg per ml at 15 min. Maximum lowering of lower esophageal sphincter pressure, −15.8 ± 3.5 mm Hg, coincided with the peak gastric inhibitory polypeptide concentrations. After pentagastrin infusion plus a 30-min intraduodenal glucose perfusion, mean serum gastric inhibitory polypeptide concentration reached a maximum of 600 ± 58 pg per ml at 30 min and remained elevated at 75 min (440 ± 39 pg per ml). These increases in serum gastric inhibitory polypeptide levels were associated with significant decrements in lower esophageal sphincter pressure with the maximum lowering occurring between 45 and 75 min (−14 to −16 mm Hg). We conclude that gastric inhibitory polypeptide lowers both basal and pentagastrin-stimulated lower esophageal sphincter pressure in cats.