Interstitial cells (ICs) may generate phasic activity (PA) in smooth muscle tissues including the bladder (1). ICs express c-kit and signalling via the tyrosine kinase gene product, kit, is essential for development of the IC phenotype. Imatinib mesylate (Glivec), a c-kit inhibitor has been widely used for studying the role of ICs in generating PA in the bladder (2 & 3). The aim of this study was to identify c-kit positive cells in pig urinary bladder using molecular, immunohistochemical (IHC) and functional techniques. The effect of imatinib on cholinergic-induced PA of the isolated pig bladder was also investigated. No ethical approval was required as female pig (≈6months old) bladders were obtained from the local abattoir. Primers were designed for the Sus scrofa c-kit mRNA and polymerase chain reaction (PCR) carried out on the c-DNA synthesized from total RNA isolated from pig bladders. PCR products were separated by electrophoresis and sequenced. For IHC studies, formalin-fixed paraffin-embedded bladder tissue was analysed using IHC staining for c-kit. Whole bladders (n=6) and their associated vasculature were surgically excised and maintained under physiological conditions, perfused with Krebs’ solution as previously described (4). The effect of intravascular administration of increasing concentrations of imatinib (1-50µM added cumulatively, 20 min exposure for each concentration) or drug vehicle on carbachol (CCh)-induced (0.1µM) whole bladder PA was monitored by recording the intravesical pressure (cmH2O). Sequencing of the PCR product confirmed the expression of c-kit mRNA in both the mucosa and detrusor layers of the pig bladder. Expression of c-kit-antigen was detected in the sub-urothelial and muscle layers of bladders by positive immunoreactivity to c-kit antibodies. Isolated pig bladders developed an increase in baseline pressure (tonic contraction) with superimposed PA in the presence of 0.1µM CCh. Intravascular imatinib had no effect on PA frequency and only the 50µM concentration significantly inhibited (41.2±8.3% inhibition, p<0.01) the amplitude of PA. However, imatinib significantly reduced (5µM: 25.5±10.7%, 10µM: 45.9±8.6 & 50µM: 95.8±8.4% inhibition, p<0.05-0.001) the tonic contraction of the isolated whole bladder. We have demonstrated c-kit expression in pig bladders using both PCR and IHC techniques. Imatinib significantly reduced the amplitude of the cholinergic-induced PA and the tonic contraction of the pig bladder with no effect on the frequency of PA. This may indicate that c-kit positive cells may play an important role in modulating the phasic contractions and the tone of the bladder in the pig.