Somatostatin effects on gastric electrolytes and pepsin in dogs with various secretory stimuli

To determine possible sites and mechanisms of action of somatostatin (SS) in gastric secretory mucosa, secretion of pepsin, H+, Cl-, Na+ and K+ was stimulated in conscious fistula dogs by i.v. infusion of bethanechol, pentagastrin and histamine in the absence and presence of SS-14. At low dose (0.5 micrograms or 300 pmol/kg/h), SS-14 potently inhibited H+ and pepsin stimulated by bethanechol (80 micrograms/kg/h) to less than 5% of control; it required 2 micrograms or 1200 pmol/kg/h of SS-14 to achieve similar inhibition of pentagastrin (1.5 micrograms/kg/h)-stimulated secretion. In both cases, gastric [K+] was depressed by SS-14 infusion and recovered before H+ and pepsin. Similar sensitivity to SS suggests a Ca++-dependent mechanism or pathway of stimulation by gastrin similar to that by cholinergic agonists. By contrast, histamine, which acts via cyclic AMP pathways, was not inhibited by a large dose of SS-14 (20 micrograms/kg/h). SS inhibition is thus agonist (or pathway)- rather than organ- or cell-specific.