Gastric acid secretion in the chicken: Effect of histamine H 2 antagonists and H +/K +-ATPase inhibitors on gastro-intestinal pH and of sexual maturity calcium carbonate level and particle size on proventricular H +/K + ATPase activity

Abstract

1. 1. Cimetidine was more potent 4hr after a single injection of 25 or lOOmg/kg body wt in increasing gastric pH than other H 2 receptor antagonists, ranitidine and famotidine but was less efficient than H +/K +-ATPase inhibitors. Omeprazole rose proventricular and gizzard pH at a lower dose than SCH 28080 and Ro 18-5364 (30, 50 and 200 mg/kg body wt, respectively). 2. 2. Proventricular and gizzard pH values were maximal 1 and 4 hr after a single injection of 7.5 μmol/kg body wt omeprazole. Inhibition of acid secretion was maintained for 24 hr after an injection of 100 μmol/kg. 3. 3. H +/K +-ATPase activity in vitro was 10μimol P i/hr/mg protein in the microsomal fractions of the proventriculus. It was doubled by nigericine and inhibited by SCH 28080. However, western blots by high specific H +/K +-ATPase monoclonal antibody 95-A3 and 95–111 recognized a 42kDa band but hardly exhibited the specific 95 kDa band recognition. 4. 4. Chickens and immature pullets showed a higher H +/K + -ATPase activity than laying hens. Calcium level of the diet did not affect the enzyme activity but coarse particles of calcium fed to pullets or laying hens enhanced the H +/K +-ATPase activity when compared with ground particles.