Comparison of urinary bladder function in 6 and 24 month male and female rats.

Micturition characteristics, collagen composition, and in vitro urinary bladder strip contractility were examined in young adult (six month) and old (24 month) male and female Fischer 344 rats. Although young female rats consumed significantly less water than young males, there were no differences in volumes of urine excreted. Old females excreted significantly more urine than old males, but there were no differences in volumes of water consumed. Old male rats had similar micturition frequencies during the light and dark cycles, in contrast to females and young males, where the number of micturitions during the dark cycle was significantly greater than those during the light cycle. The mean and maximal micturition volumes were significantly greater in old males compared to young males and old females during both the light and dark cycles. Bladders from female rats weighed significantly less than bladders from males of the same age, and the bladders from young rats weighed less than those of old rats. The protein and collagen concentrations were significantly less in bladder bodies from young females than old females. The amount of collagen resistant to digestion by Pronase, and thus thought to be cross-linked, was significantly greater in bladders from old rats compared to young. No differences between groups were found in the contractile responses of bladder base strips. There were trends for the absolute contractile responses of bladder body strips from old males to field stimulation, carbachol, ATP, and KCl to be larger than the other groups, and for strips from the young females to be smaller. The responses of strips from young females to field stimulation and KCl were significantly less than those of young males or old females, and responses to 10(-3) M ATP were less than those of old females. Responses of strips from old males to 60 mM KCl were significantly greater than those of young males. The differences in contractility could be attributed to the differences in strip mass. It appears, therefore, that urinary bladder function in male and female rats is unaffected by increasing age between 6 and 24 months.