Objectives: To provide sensitive physiological endpoints for the onset and long-term progression of deficits induced by diabetes mellitus (DM) in bladder and erectile function in male rats, and to evaluate parallel changes in urogenital and nerve function induced by hyperglycaemia over a protracted period as a model for chronic deficits in patients with diabetes.
Materials and methods: The study comprised in 877 male, 3-month-old, Fischer 344 rats; 666 were injected intraperitoneally with 35 mg/kg streptozotocin (STZ) and divided into insulin-treated and untreated diabetic groups. The rats were studied over 8 months and measurements made of both erectile and bladder function, as well as nerve conduction studies over the duration of the study.
Results: There was an early (first month) abnormality of both erectile and bladder function that persisted through the 8 months of the study. The erectile dysfunction was manifest as reduced intracavernous pressure/blood pressure ratio, and the bladder dysfunction as a persistent increase in detrusor overactivity with no detrusor decompensation. Insulin treatment prevented or modified the abnormality in each organ. Hyperglycaemia caused a progressive decrease in caudal nerve conduction velocity. The mean digital sensory and tibial motor nerve conduction velocity did not deteriorate over time. Correlation measurements of nerve and organ function were not consistent.
Conclusions: The results of this extensive long-term study show early and profound effects of hyperglycaemia on the smooth muscle of the penis and bladder, that were persistent and stable in surviving rats over the 8 months. The physiological changes did not correlate well with neurological measurements of those organs. Significantly, diverse smooth-muscle cellular and subcellular events antedated the measured neurological manifestations of the hyperglycaemia by several months. Although autonomic diabetic neuropathy is a primary life-threatening complication of long-term diabetes in humans, this rat model of STZ-induced diabetes showed that the rapid onset of physiological manifestations was based on many molecular changes in the smooth muscle cells in this model of type 1 DM.