The regulation of gastrin secretion in the chicken

Chicken gastrin has a C-terminal sequence resembling mammalian cholecystokinin, but its biological properties resemble mammalian gastrin. The mechanisms controlling chicken gastrin release are poorly understood. We have investigated the factors which influence chicken gastrin secretion in vivo. Plasma gastrin concentration was decreased within 12 h of fasting, but tissue gastrin concentrations were not significantly changed even after 24 h of food deprivation. In birds fasted for 24 h and treated with the H+/K(+)-ATPase inhibitor, omeprazole, plasma gastrin concentration was greatly enhanced indicating the importance of acid inhibition of the gastrin cell. It is well established that amino acids (particularly aromatics like Phe and Trp) and peptides stimulate gastrin release in mammals. In chicken, however, Met, His and Arg were the strongest stimulant amongst the essential amino acids investigated. Of these three amino acids, Met rapidly stimulated gastrin release. The GRP antagonist M216140 did not suppress the Met-induced gastrin release, suggesting that Met did not stimulate GRP release. Aromatic amino acids did not strongly influence gastrin release. Medium chain triacylglycerol, which is rapidly hydrolyzed to fatty acids in the lumen, strongly stimulated gastrin secretion but long chain triacylglycerol had no effect. The data suggest that amino acids (Met, Arg and His) and fatty acids, but not triacylglycerol, are gastrin releasing factors in birds while acid inhibits secretion: there are therefore both similarities and differences between birds and mammals in the control of gastrin release.