CHANGES IN BLADDER FUNCTION IN THE ONE YEAR SPONTANEOUSLY DIABETIC BB RAT

Micturition characteristics and in vitro urinary bladder function were investigated in insulin-treated spontaneously diabetic BB rats and age-matched non-diabetic controls one year after the onset of diabetes. BB rats weighed less than controls and were hyperglycemic. Diabetic rats consumed larger volumes of water and excreted larger volumes of urine than controls. The frequency of micturitions and the mean volumes of urine excreted per micturition were significantly increased in BB rats compared to age-matched controls. Associated with the micturition changes in the BB rats were significant increases in bladder body mass. Contractile responses of strips from bladder bodies and bases were measured in response to nerve stimulation, carbachol, phenylephrine, ATP, and KCl. No significant differences between controls and diabetics were found in the absolute contractile responses of bladder body strips to nerve stimulation, carbachol, ATP, or KCl. However, if the data were transformed to correct for the increases in tissue mass in the diabetics, there were significant decreases in the responses of bladder body strips from BB rats to carbachol. ATP, and KCl, but not to nerve stimulation. Even after transformation, there were no differences in the responses of bladder base strips to carbachol, phenylephrine, or KCl. The data indicate that significant changes in micturition characteristics are evident one year after the onset of diabetes in the spontaneously diabetic BB rat. These changes are slow in development, since they are absent six months after the onset of diabetes. The changes in micturition and bladder strip contractility are qualitatively similar to, but quantitatively modest in comparison with those caused by streptozotocin-induced diabetes mellitus. The quantitative differences are probably attributable to an ameliorative effect of the insulin received by the BB rat.