Effect of hydrogen peroxide on contractility and citrate synthase activity of the rabbit urinary bladder in the presence and absence of resveratrol and a whole-grape suspension.

One etiology related directly to obstructive urinary bladder dysfunction is ischemia/reperfusion resulting in significant oxidative stress to the bladder. Grapes, a natural source of antioxidants, have been proven effective in preventing obstructive and ischemic bladder dysfunction. Many investigators believe that resveratrol is the primary active antioxidant ingredient in grapes. We compared the ability of a whole-grape suspension with pure resveratrol in their ability to protect the bladder from in vitro oxidative stress mediated by hydrogen peroxide (H2O2). Four male rabbit bladders were used. Two strips from each bladder were incubated in the presence of 1 mg/mL grape suspension for 30 min, another two strips were incubated in the presence of 1 mg/mL resveratrol solution, and the last two strips were incubated in the presence of 1 mg/mL sucrose/and fructose as controls. The rest of the bladder was separated into muscle and mucosa, frozen and stored for biochemical evaluation. (1) Chemically, resveratrol has about 20 times the antioxidant capacity of the grape suspension. (2) The grape suspension had significant protective effects when the rate of tension was quantitated at all concentrations of H2O2, while the resveratrol had no effect. (3) Citrate synthase activities of the muscle and mucosa were significantly protected by the grape suspension but not by resveratrol. These data demonstrate that the grape suspension protects the mitochondria to a significantly greater degree than resveratrol, which suggests that the antioxidant activities are due to the combination of active components found in the grape suspension and not just resveratrol.