Evidence for the role of mast cells in colon-bladder cross organ sensitization

This study examined the contribution of mast cells to colon-bladder cross organ sensitization induced by colon irritation with trinitrobenzene sulfonic acid (TNBS-CI). In urethane anesthetized rats 12. days after TNBS-CI, the voiding interval was reduced from 357. s to 201. s and urothelial permeability, measured indirectly by absorption of sodium fluorescein from the bladder lumen, increased six-fold. These effects were blocked by oral administration of ketotifen (10. mg/kg, for 5. days), a mast cell stabilizing agent. TNBS-CI in wild type mice produced a similar decrease in voiding interval (from 319. s to 209. s) and a 10-fold increase in urothelial permeability; however this did not occur in Kit^aW^a/Kit^aW-v^a mast cell deficient mice. Contractile responses of bladder strips elicited by Compound 48/80 (50 μg/ml), a mast cell activating agent, were significantly larger in strips from rats with TNBS-CI (145% increase in baseline tension) than in control rats (55% increase). The contractions of strips from rats with TNBS-CI were reduced 80-90% by pretreatment of strips with ketotifen (20 μM), whereas contractions of strips from control animals were not significantly changed. Bladder strips were pretreated with SLIGRL-NH2 (100 μM) to desensitize PAR-2, the receptor for mast cell tryptase. SLIGRL-NH2 pretreatment reduced by 60-80% the 48/80 induced contractions in strips from rats with TNBS-CI but did not alter the contractions in strips from control rats. These data indicate that bladder mast cells contribute to the bladder dysfunction following colon-bladder cross-sensitization.