Response to vasoconstrictor agents by detrusor smooth muscles from cisplatin-treated rats and antioxidant treatment.

The effects of melatonin and quercetin on the contractile responses of cisplatin-treated rat detrusor smooth muscle were tested. Detrusor strips obtained from four separate rat groups (control, cisplatin, melatonin+cisplatin and quercetin+cisplatin) were mounted in 25 mL organ baths containing Krebs-Henseleit solution (KHS) at 37°C, continuously gassed with 95% O₂ and 5% CO₂. The vasoconstriction induced by acetylcholine (ACh) and potassium chloride (KCl) were compared within the groups. Furthermore, histopathological parameters such as edema, congestion, inflammatory cells, microvascular proliferation, fibrosis, eosinophil, mast cells and epithelial damage were noted. In routine experiments ACh and KCl triggered concentration-dependent contractions. Pretreatment with cisplatin increased the sensitivity but not the maximal response to ACh and KCl. In rats treated with melatonin or quercetin before cisplatin, the EC₅₀ values, but not the maximal response, to both agents were significantly higher than in the cisplatin-treated (CII) group. Histopathological parameters such as edema, congestion, inflammatory cells, microvascular proliferation, fibrosis, eosinophil, mast cells and epithelial damage were all higher in the cisplatin-treated group than in the controls. Melatonin pretreatment significantly decreased mast cell numbers and epithelial damage when compared to cisplatin treatment alone but these effects were not recorded with quercetin pretreatment. These results demonstrate for the first time that melatonin can attenuate urinary bladder injury produced by cisplatin treatment.