Diabetes induced alterations of M3-muscarinic receptors (M3-mAChR) in the urothelium and muscle layer of the urinary bladder were studied using streptozotocin (STZ)-induced diabetic rats. Male Wistar rats were divided into two groups; group I: normal control rats; group II: STZ-induced diabetic rats, 2 weeks after induction. The bladder was divided into urothelium and muscle layer by microdissection. Tissue M3-mAChR protein levels were measured by Western blotting. Expression of the mRNA that encoded M3-mAChR was estimated using the method of reverse transcription combined with polymerase chain reaction (RT-PCR). M3-mAChR protein and mRNA expressions were found in both the urothelium and muscle layer of the rat urinary bladder. In control rats, the M3-mAChR protein expression ratio in the urothelium and muscle layer was 1:1.87; that for mRNA was 1:0.74. Two weeks after induction of diabetes, the M3-mAChR mRNA expression in the urothelium and muscle layer were significantly increased by 45.7% (P < 0.01, n = 8) and 80.8% (P < 0.001, n = 8), respectively. Correspondently, the bladder M3-mAChR protein levels were significantly increased by 50.0% (P < 0.01, n = 8) in the urothelium and 147.1% (P < 0.001, n = 8) in the muscle layer of the diabetic rats. In conclusion, M3-mAChR mRNA and protein are expressed in both the urothelium and muscle layer of the rat urinary bladder. STZ-induced diabetes increases mRNA and protein expression of the M3-mAChR in the urothelium as well as the muscle layer.
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