Effect of somatostatin on ion transport in the rat colon.
The effect of somatostatin (SRIF) on ion transport was determined in the rat colon in vitro. SRIF produced a sustained decrease in the short circuit current (Isc) (-0.8 +/- 0.1 mueq/h x cm2) and increased net Cl absorption (0.9 +/- 0.3 mueq/h x cm2). The threshold effect of SRIF on Isc was observed at 6 nM. 10 microM serotonin decreased net Na absorption (-2.6 +/- 0.4 mueq/h x cm2), net Cl absorption (-3.6 +/- 0.5 mueq/h x cm2) and increased Isc (0.7 +/- 0.1 mueq/h x cm2); these changes were totally blocked by 0.1 microM SRIF. SRIF completely blocked net Cl secretion induced by 10 mM theophylline (-2.5 +/- 0.7 to +4.1 +/- 2.0 muq/h x cm2) and partially blocked theophylline-induced inhibition of net Na absorption (0.7 +/- 0.5 to 2.1 +/- 0.4 mueq/h x cm2). SRIF also blocked prostaglandin E1 (PGE1) induced increase in potential difference and Isc (P < 0.001). Mucosal cyclic AMP levels were increased by theophylline and PGE1 but not by serotonin. SRIF had no effect on basal or theophylline- and PGE1-stimulated cyclic AMP levels. These results indicate that SRIF blocks both cyclic AMP and noncyclic AMP mediated changes in ion secretion and suggest that SRIF is acting at a step in the secretory process beyond the formation of cyclic AMP.
D000042:Absorption; D000818:Animals; D001692:Biological Transport; D002712:Chlorides / Q000378:metabolism*; D003106:Colon / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism; D066298:In Vitro Techniques; D007413:Intestinal Mucosa / Q000378:metabolism; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D011458:Prostaglandins E / Q000494:pharmacology; D051381:Rats; D012701:Serotonin / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism*; D013004:Somatostatin / Q000494:pharmacology*; D013806:Theophylline / Q000494:pharmacology
D002712:Chlorides; D011458:Prostaglandins E; D012701:Serotonin; D013004:Somatostatin; D012964:Sodium; D013806:Theophylline; D000242:Cyclic AMP