Altered regulation of intestinal ion transport by enteric nerves in diabetic rats
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We compared ion transport parameters in isolated ileal mucosa from diabetic rats (8 wk after streptozotocin injection) and littermate controls under basal conditions and in response to electrical transmural stimulation (TS). Stripped ileal mucosa (submucosal plexus intact) was mounted in Ussing flux chambers modified to include stimulating electrodes on opposite sides of the tissue. Under basal conditions unidirectional fluxes of Na+ and Cl- were decreased across mucosa from diabetic rats compared with controls, whereas net fluxes were not significantly different. TS caused a tetrodotoxin (TTX)-sensitive transient increase in short-circuit current (Isc) that was significantly less in tissue from diabetic than control rats. The muscarinic cholinergic receptor antagonist, atropine, significantly reduced the Isc response to TS in ileum from control but not diabetic rats. In addition, the noncholinergic component of the response was smaller. The muscarinic agonist, Urecholine chloride (bethanechol chloride), caused an increase in Isc that was unaffected by pretreatment with TTX and was the same in tissue from control and diabetic rats. Our results suggest that the intestinal abnormalities that occur in diabetes may include a defect in the regulation of ion transport by enteric nerves resulting in an abnormal ability to respond to luminal and other stimuli.
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