Time-dependent bladder activity changes in streptozotocin-induced female diabetic rats

This study aimed to investigate the long-term physiological and morphological changes in the bladders of diabetic rats. Sixty-nine female Sprague-Dawley rats were divided into a control and six diabetic (3 days and 2, 4, 8, 12, and 24 weeks after induction of type 1 diabetes) groups. Metabolic cages and cystometry were used to evaluate bladder function. Bladder contractility was assessed using an organ bath test, and Masson's trichrome staining was performed. In the metabolic cage study, the urination frequency during the dark period significantly increased in the early stages at 3 days of diabetes (p < 0.05). The voiding interval significantly increased (p < 0.05) at 8-12 weeks of diabetes, while the residual urine volume and voiding efficiency worsened at 24 weeks. In the organ bath study, the dose-response curve of carbachol for median effective concentration did not change; however, the bladder contractile force was enhanced at 8 weeks (p = 0.028). Histological analysis revealed increased fibrosis at 4 weeks of diabetes. Diabetic bladder dysfunction is characterized by storage and voiding bladder activity changes in the early stages that induces urinary frequency and reduced voiding efficiency in the late phase; this turning point occurs at 8 weeks after diabetes.