Inhibitory effect of sorbin on pepsin secretion in conscious cats and rabbits.

Sorbin, a 153 amino acid polypeptide isolated from porcine upper small intestine and its shortest synthetic derivative, the C-terminal heptapeptide (C7-sorbin), substituted by D alaninamide in the last position (D7-sorbin), have proabsorptive and antisecretory effect in the different parts of the intestine. We showed that labeled C7-sorbin accumulated not only in the enterocytes and the enteric nervous system but also in the gastric chief cells in the rat. The chief cell secretion of pepsin was then studied in two other species, the cat and the rabbit, simultaneously with the acid secretion of parietal cells. Lipase secretion was studied in the rabbit because lipase is exclusively secreted by the upper cells of the fundic glands, which do not secrete pepsin. The animals were equipped with a gastric fistula, fully innervated, and a Heidenhain pouch, vagally denervated, during a continuous perfusion of pentagastrin (PG) 2 microg/kg. h and vasoactive intestinal peptide (VIP) 4 microg/kg. h. D7-sorbin (100 pmol/kg. h) inhibited cat and rabbit pepsin secretion from the innervated gastric fistula secretion and from the cat denervated Heidenhain pouc secretion, but was without effect on acid secretion and lipase secretion. These data indicate that the inhibitory effect of sorbin is specific on chief cells because the acid parietal cell secretion in both species and lipase upper cell secretion of the fundic glands, in the rabbit, are not implicated.

Cholinergic and pentagastrin stimulation of the gastric secretions of acid, pepsin and lipase in the awake rabbit.

Acid, pepsin and lipase secretions were simultaneously studied in awake rabbits with a Heidenhain pouch during cholinergic (carbamylcholine 20 micrograms.kg-1 x h-1) or maximal pentagastrin stimulation (64 mu.kg-1 x h-1). To avoid lipase inactivation by low pH, the pouch was perfused at a constant pH, with a solution irrigating the pouch without inducing any pressure. Acid and pepsin outputs were equally activated by both stimulants. Lipase output was stimulated much more by pentagastrin (x26) than by carbamylcholine (x6). The maximal lipase output preceded that of acid output. Lipase concentration increased in the gastric juice whereas pepsin concentration remained constant. A negative correlation was calculated between acid and lipase or pepsin and lipase output. A positive correlation was obtained between acid and pepsin. Our data show that pepsin and lipase secretions which come from distinct chief cells, in the rabbit, responded to the same stimulants but with quantitative and timing differences.