EFFECTS OF AGING AND X-IRRADIATION ON THE DIURNAL RHYTHM OF MOUSE URINARY-BLADDER CAPACITY

The effect of single-dose irradiation (19 Gy) or sham treatment on cir cadian variations in urinary bladder storage capacity was assessed dur ing a 250-day period following treatment using transurethral cystometr y under anesthesia. Changes in bladder function were quantified as the deviation from individual pretreatment values of bladder volume at de fined intravesical pressures. A marked diurnal rhythm with a peak at 1 9.00 h and an extended nadir between 1.00 h and 12.00 h was found in 1 1- to 12-week-old untreated mice. No systematic changes in bladder fun ction with age could be observed in repeated cystometries after sham t reatment. X-Irradiation resulted in a triphasic response. After an ear ly reversible decrease in bladder capacity (acute phase) complete reco very was observed within 30 days after irradiation. Following a sympto m-free latent period of about 15 weeks, chronic progressive impairment of bladder storage function developed (chronic phase). During the acu te and latent period, no changes in the diurnal pattern were observed. In the late phase, not only a decrease in the absolute capacity value s but also in the amplitude of diurnal fluctuations was seen. The dail y minimum values, however, were still found between 1.00 and 12.00 h. The data indicate that cystometry values obtained between 8.00 and 12. 00 h provide suitable parameters for the quantification of radiation e ffects in the urinary bladder in longitudinal studies.