Effects of diabetes mellitus on the biomechanical properties of the female rat urethra

The effects of diabetes mellitus (DM) on bladder function are well described, but little is known of effects on the outlet function of the urethra. In the present study, biomechanical properties of urethras from DM and healthy female rats were compared. At 3, 5, and 10 weeks following streptozotocin induction of DM, urethras were excised from anesthetized rats maintaining in vivo length, mounted onto tees at in vivo length in an established ex vivo vascular testing system, and maintained in an oxygenated circulating bath of physiological media at 37°C. Stepwise intraurethral pressure increments from 0-20 mmHg were applied and diameters were simultaneously recorded at proximal, mid, and distal positions. Urethras from age-matched rats served as controls. There was a proximal-distal decreasing gradient in compliance in normal urethras, and a progressive increase in beta stiffness from 3-10 weeks following DM in the mid and proximal regions to values indistinguishable from the distal. Increasing urethral stiffness in DM results in a collapse of the compliance gradient leading to increased outlet resistance for a bladder in which contractility is already compromised. Thus, DM effects on the urethra interact with those on the bladder to further compromise lower urinary tract function.