DISTURBED PYLORIC MOTILITY IN WS WS MUTANT RATS DUE TO DEFICIENCY OF C-KIT-EXPRESSING INTERSTITIAL-CELLS OF CAJAL/

Interstitial cells of Cajal (ICC) are believed to initiate the basic c ontractile activity of the gastrointestinal tract. Interstitial cells of Cajal express c-kit receptor tyrosine kinase and are deficient in W s/Ws mutant rats with a small deletion of the c-kit gene. As Ws/Ws rat s show remarkable bile reflux to the stomach, the contraction pressure of the pylorus was compared between Ws/Ws and control +/+ rats. The c ontraction pressure of the pylorus was measured using a microtransduce r, which was inserted through a pin-hole in the anterior wall of the s tomach under anesthesia. The magnitude of bile reflux was estimated by measuring the content of bile acids in the stomach. The c-kit messeng er RNA-expressing cells were detected by in situ hybridization. Freque ncy and the maximum pressure of the contraction were comparable betwee n Ws/Ws and +/+ rats, but the duration of the contraction was signific antly shorter in Ws/Ws rats than in +/+ rats. The number of c-kit mess enger RNA-expressing ICC in the pylorus of Ws/Ws rats was 1.7% that of +/+ rats. The bile reflux observed in Ws/Ws rats was attributed to th e decrease in the duration of the pyloric contraction, which appeared to result from the deficiency of c-kit messenger RNA-expressing ICC.