Somatostatin-14 and -28: clearance and potency on gastric function in dogs

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Abstract
The significance of somatostatin-14 (S-14) and somatostatin-28 (S-28) in gastric physiology, was examined to compare their relative potencies on acid secretion in the dog. On a molar infusion basis, S-14 and S-28 appeared to be equipotent, causing 50% inhibition of peptone meal-stimulated acid secretion at a dose of 400 pmol.cntdot.kg-1.cntdot.h-1. Comparison of the plasma half lives (t1/2) of the 2 peptides revealed that S-28 disappeared at a much slower rate (t1/2 = 2.84 .+-. 0.15 min, mean .+-. SE, n = 7) than S-14 (t1/2 = 0.57 .+-. 0.06 min). When acid-inhibitory effect was compared against increment in plasma concentrations produced by peptide infusion, S-14 was roughly 10-fold more potent than S-28. No alteration of gastrin response to peptone was observed at a dose of S-14 or S-28 that completely abolished acid secretion, suggesting that regulation of acid secretion is not mediated by gastrin inhibition. S-14 is a potent and possibly important physiological inhibitor of gastric acid secretion. Although circulating S-28 may have importance in regulation of some biological functions, it appears to play a less prominent role in regulation of gastric secretion.