Phytohaemagglutinin inhibits gastric acid but not pepsin secretion in conscious rats

Phytohaemagglutinin (PHA), a kidney bean lectin, is known for its binding c apability to the small intestinal surface. There has been no data available , however, on the biological activity of PHA in the stomach. Recent observa tions indicate that PHA is able to attach to gastric mucosal and parietal c ells. Therefore, we examined whether PHA affects gastric acid and pepsin se cretion in rats. Rats were surgically prepared with chronic stainless steel gastric cannula and with indwelling polyethylene jugular vein catheter. Du ring experiments, animals were slightly restrained. Gastric acid secretion was collected in 30 min periods. Acid secretion was determined by titration of the collected gastric juice with 0.02 N NaOH to pH 7.0. Pepsin activity was estimated by measuring enzymatic activity. Saline, pentagastrin and hi stamine were infused intravenously. PHA or bovine serum albumin (BSA) were dissolved in saline and given intragastrically through the gastric cannula. PHA significantly inhibited basal acid secretion. Inhibition of acid outpu t reached 72% during the first collection period following PHA administrati on when compared, then gradually disappeared. Pentagastrin-stimulated acid secretion was repressed dose-dependently by PHA as well. Maximal inhibition was observed during the first 30 min following application of PHA. Histami ne-stimulated acid secretion was inhibited by PHA in a similar manner. Peps in secretion was not affected by PHA under either basal or stimulated condi tions. These results provide evidence that PHA is a potent inhibitor of gas tric acid secretion in conscious rats, but it does not affect pepsin output from the stomach. (C) 2001 Elsevier Science Ltd. All rights reserved.