ENDOGENOUS FACTORS MODULATING URINARY-BLADDER COMPLIANCE IN MICE

The application of repeated cystometric measurements in longitudinal l ong-term studies both in patients and experimental animals requires de tailed knowledge of factors causing intraindividual variability. In th e present study, the effect of age, body weight, estrus cycle phase, r ectal temperature and premeasurement bladder volume on the results of cystometry in mice have been assessed. No systematic changes in bladde r compliance parameters were observed with age (75 to 344 days) or bod y weight (18 to 38 gm.). Also, the animal's position in the estrus cyc le had no effect on bladder capacity. The abdominal temperature, adjus ted to 32 to 37.3C under anesthesia, did not affect the outcome of cys tometry either. When the bladder was emptied at 1.5 to 3.5 hours befor e cystometry, a significant drop in bladder capacity to about 60% of i ndividual control values was observed. This initial emptying clearly d ecreased the intraindividual variability in absolute terms (standard d eviation), but not the relative variability (coefficient of variance). Thus only a shift in absolute values, but no improvement in reproduci bility of cystometric results, could be achieved. Bladder filling to 1 0 or 25 mm. Hg 40 minutes to 2 hours before cystometry increased the b ladder capacity to 120 or 145%, respectively, when anesthesia was main tained throughout the experiment. When intervals longer than 2 hours w ere studied, animals were allowed to regain consciousness between init ial bladder filling and cystometry. Under these conditions, the capaci ty data returned to normal or subnormal values.