The influence of diabetes mellitus on glucose utilization by the rat urinary bladder

Streptozocin-induced diabetes in rats causes changes in urinary bladder function and increases the responsiveness of isolated bladder strip preparations to contractile agents and field stimulation. We monitored the role of extracellular glucose in the contractile responsiveness of bladder body strips from control, 2-month diabetic, and sucrose-drinking rats to the muscarinic agonist bethanechol. Consumption of sucrose and induction of diabetes caused increases in bladder mass compared with that of controls. In the presence of normal glucose levels (5.6 mmol/L), bladder strips from diabetic rats responded to bethanechol with significantly larger responses than those from control or sucrose-drinking rats. Removal of glucose from the bathing medium caused time-dependent decreases in contractile response of bladder strips from all groups; there were no differences in the percent decrease in response between the three groups. The presence of insulin (100 mU/mL) had no effects on contractile responsiveness or the rate of decline of response. Following return of glucose to the medium, there were progressive increases in contractile responsiveness in all groups, which returned to original contractile values within 60 minutes and were unaffected by insulin. Pyruvate (9.1 mmol/L) was able to substitute for glucose in maintaining the contractile responses. Increasing the glucose concentration of the medium to 30 mmol/L had no effects on contractile responses. Unstimulated bladder adenosine triphosphate (ATP) and creatine phosphate concentrations were similar in control, diabetic, and sucrose-drinking rats. In conclusion, changes in glucose utilization and high-energy phosphate levels cannot explain the increased contractile responsiveness of bladder body strips from diabetic rats to contractile agents.