Beneficial effect of preconditioning on ischemia-reperfusion injury in the rat bladder in vivo.

We investigated the effect of preconditioning on ischemia-reperfusion injury in the rat bladder. Rat abdominal aorta was clamped with a small clip to induce ischemia-reperfusion injury in the bladder. Twelve-week-old male SD rats were divided into three groups; sham-operated control (Cont), 30 min ischemia-60 min reperfusion (IR) and three times of 5 min ischemia and then 30 min ischemia-60 min reperfusion (PC) groups. The bladder functions were estimated by cystometric and functional studies. Contractile response curves to increasing concentrations of carbachol were constructed in the absence and presence of various concentrations of subtype selective muscarinic antagonists, i.e. atropine (non-selective), pirenzepine (M1 selective), methoctramine (M2 selective), and 4-DAMP (M1/M3 selective). We also measured tissue levels of malonaldehyde (MDA) and examined possible histological changes in these rats' bladders. Preconditioning partially prevented the reduction of bladder dysfunction induced by ischemia-reperfusion. Estimation of the pA2 values for atropine, pirenzepine, methoctramine, and 4-DAMP indicates that the carbachol-induced contractile response in bladder dome is mediated through the M3 receptor subtype in all groups. The MDA concentration in the IR group was significantly larger than that of the control group, and preconditioning significantly reduced MDA production in the bladder. In histological studies, the ischemia-reperfusion with or without preconditioning caused infiltration of leukocytes and rupture of microcirculation in the regions of submucosa and smooth muscle without a corresponding sloughing of mucosal cells. Our data indicate that preconditioning has a beneficial effect on ischemia-reperfusion injury in the rat bladder.

N-hexacosanol prevents diabetes-induced rat ileal dysfunction without qualitative alteration of the muscarinic receptor system.

We evaluated the effects of N-hexacosanol, a cyclohexenonic long-chain fatty alcohol, on muscarinic receptors in diabetic rat ileal dysfunction. Eight-week-old male SD rats were divided into four groups. After induction of diabetes (streptozotocin 50 mg/kg, i.p.), three groups were maintained for eight weeks with treatment by N-hexacosanol (0, 2 or 8 mg/kg, s.c. every day). Ileum function was investigated by organ bath studies using carbachol and KCl, and the expression levels of muscarinic M(2) and M(3) receptors were investigated by real-time polymerase chain reaction. Various concentrations of subtype-selective muscarinic antagonists, i.e., atropine (non-selective), pirenzepine (M(1) selective), methoctramine (M(2) selective), and 4-diphenylacetoxy-N-methylpiperidine methiodide (4-DAMP, M(1)/M(3) selective), were used in this study. In the presence and absence of these antagonists, contractile response curves to increasing concentrations of carbachol were investigated. Treatment with N-hexacosanol did not alter the diabetic status of the rats, but did significantly prevent the carbachol-induced hypercontractility in diabetic rat ileum. Estimation of the pA(2) values for atropine, pirenzepine, methoctramine, and 4-DAMP indicated that the carbacholinduced contractile response in the ileum is mainly mediated through the muscarinic M(3) receptor subtype in all groups. Furthermore, N-hexacosanol significantly prevented the diabetes-induced up-regulation of intestinal muscarinic M(2) and M(3) receptor mRNAs in streptozotocin-diabetic rats. Our data indicated that N-hexacosanol exerts preventive effects with respect to carbachol-induced hypercontractility in the diabetic rat ileum without qualitative alteration of the muscarinic receptor system.