EFFECT OF MUCOSAL REMOVAL ON THE RESPONSE OF THE FELINE BLADDER TO PHARMACOLOGICAL STIMULATION

The urothelium plays an important role in the maintenance of normal bl adder function. It provides a nonpermeable barrier to the contents of urine. The urothelium is directly involved in the transduction of both intravesical pressure and intravesical volume information to the affe rent nerve fibers located within the lamina propria area. A third func tion may be to modulate bladder contractile function through local sec retion of bioactive substances into the muscularis layers adjacent to the urothelium. To test this last hypothesis, the following experiment s were performed: Strips of female cat bladders were isolated from the bladder body, base and urethra. The mucosa of alternate adjacent stri ps was removed, and the contractile response to field stimulation (FS) , bethanechol (body), phenylephrine (base, urethra) and KCl was determ ined. For the bladder body, the strips without mucosa responded to FS, bethanechol, adenosine triphosphate (ATP) and KCl significantly great er than the strips with mucosa intact. For the bladder base and urethr a, the contractile responses to FS, KCl and phenylephrine were signifi cantly greater for the strips with mucosa removed as compared with the strips with mucosa intact. For the urethra and bladder base, FS in th e presence of phenylephrine produced a relaxation. For the bladder bas e, the degree of FS relaxation of the isolated strips with mucosa remo ved was significantly greater than the strips with mucosa intact. For the urethra, FS relaxation was similar for the two groups. In conclusi on, removal of the urothelium significantly and substantially increase d the contractile response to FS, KCl, bethanechol and phenylephrine. Field stimulation relaxation in the bladder base was also enhanced. Th us in the cat, the mucosa has a significant inhibitory effect on the c ontractile response of the bladder to stimulation. The mechanism of th is activity is not clear at the present time but will be the subject o f further study.