DECREASE IN INTRAVESICAL SALINE VOLUME DURING ISOVOLUMETRIC CYSTOMETRY IN THE RAT

This study was undertaken to examine the change in intravesical saline volume during isovolumetric cystometry in the urethane anesthetized f emale rat. The ureters were transected bilaterally and their distal en ds were ligated. To prevent leakage of intravesical fluid, the proxima l urethra was ligated after inserting a urethral catheter into the bla dder. In 13 rats in which the bladder was filled with different Volume s of saline between 0.3 and 2.0 mi and maintained under isovolumetric conditions for 3 hours, intravesical volume decreased (4 - 79%) when i nitial intravesical saline volume was equal to or greater than 0.6 ml (n = 9). In 9 rats in which intravesical volume decreased, mean final volume was 0.68 +/- 0.09 ml. The percentage change in intravesical vol ume (y) significantly depended on initial volume (x) (y = -42x + 17, n = 13). In 7 rats in which the proximal urethra was ligated and the bl adder was filled with different volumes of soybean oil between 0.25 an d 2.0 ml, intravesical volume did not change. In 8 rats in which the b ladder neck was ligated around a urethral catheter to block blood flow to the bladder and in which the bladder was filled with different vol umes of saline (0.3-1.8 ml), intravesical volume decreased when initia l volume was equal to or greater than 1.35 mi. These results demonstra te that intravesical saline is absorbed from the normal bladder wall w hen intravesical volume is greater than the volume (0.6 ml) necessary to evoke the micturition reflex in urethane anesthetized rats. (C) 199 7 Wiley-Liss, Inc.