Alterations in urinary bladder M₂-muscarinic receptor protein and mRNA in 2-week streptozotocin-induced diabetic rats

The M₂ receptor (M₂-mAChR) is quantitatively the dominant muscarinic subtype in animal bladders. The alterations in its protein quantity and biosynthesis during diabetic cystopathy were investigated. Three-month-old male Wistar rats were divided into two groups: (1) 2-week-old diabetics; and (2) normoglycemic control rats. Diabetes was induced by single intravenous injection of 60 mg/kg streptozotocin. The amount of M₂ receptor protein in the rat bladder body tissue was measured by Western immunoblotting using monoclonal antibodies. For determination of M₂ muscarinic receptor mRNA in the bladder tissue, the method of Northern blotting was employed. The results of the Western immunoblotting showed that the amount of M₂-mAChR protein in the diabetic bladder was significantly increased by 40.0±6.2% when compared with the control bladder (P<0.05, n=8). The Northern blotting demonstrated a 69.3±8.5% increase of the M₂-mAChR mRNA in the diabetic bladder (P<0.05, n=8). The findings of the present study demonstrated an up-regulation of M₂-mAChR biosynthesis in the diabetic urinary bladder. This phenomenon could lead to increased reactivity to acetylcholine and thus results in detrusor instability. Copyright (C) 1999 Elsevier Science Ireland Ltd.