Evaluation of the secretory response to endogenous and exogenous prostaglandins in mucosa from the proximal and distal portions of the colon of dogs

Abstract

To compare secretory responses to prostaglandin (PG) E(2) in mucosa obtained from the proximal and distal portions of the colon of dogs. Colonic mucosa from cadavers of 18 clinically normal adult dogs. Short-circuit current (I(SC)) and maximum change in I(SC) (ΔI(sc)) in response to administration of 1μM PGE(2) were measured across mucosa obtained from the proximal and distal portions of the colon. Responses were evaluated in mucosa (n = 6 dogs) incubated in Ussing chambers with or without 1 mM amiloride or without chloride in the Ringer's bathing solution. Responses were also evaluated in mucosa (n = 9 dogs) incubated with or without pretreatment with 1 μM indomethacin, with or without amiloride in the subsequent bathing solution. Histologic changes in mucosa from 3 dogs were assessed over time. I(SC) and ΔI(SC) were significantly reduced when chloride was removed from, but not when amiloride was added to, the bathing solution and were significantly reduced after pretreatment with indomethacin. The ΔI(SC) was significantly greater in mucosa from the distal portion of the colon than in the proximal portion of the colon. Histologic changes after incubation for 3 hours were minimal. I(SC) and ΔI(SC) resulted from electrogenic chloride secretion. Chloride secretion was reduced when release of PGs was prevented by indomethacin and was induced by administration of PGE(2). Chloride secretion in response to PGE(2) was greater in mucosa from the distal portion of the colon than in mucosa from the proximal portion of the colon.