Effects of aging on mitochondrial enzyme activity of rat urinary bladder

Objectives: Our previous study showed that aged rat bladders became fatigue d faster than young bladders following repeated contraction induced by elec trostimulation, One factor might be a lower energy-producing capability sec ondary to a decreased mitochondrial enzyme activity of the aged bladder. Th is study examined this possibility. Materials and Methods: Mitochondria fro m 3- (n = Il) and 24-month-old (n = 10) Sprague-Dawley rats were isolated. Activities of the following enzymes were assayed: two key enzymes in the ci tric acid cycle, citrate synthase and malate dehydrogenase, and three enzym es in the respiratory chain reaction, NADH-cytochrome c reductase, succinat e-cytochrome c reductase and cytochrome c oxidase, The concentration of pho sphocreatine and ATP in the aged rat bladders and a separate group of young bladders (n = 12) was determined using high-performance liquid chromatogra phy, Results: (1)The aged bladders have a significantly lower level of phos phocreatine and ATP content than those of young bladders. (2) The activitie s of all five enzymes assayed were significantly lower in the aged bladders than in young bladders, especially for citrate synthase, which had only 46 .8% of the activity of young bladders. Conclusions: Aging reduces the mitoc hondrial enzyme activity of the rat bladder resulting in a lower energy-pro duction capability, which might explain some of the voiding dysfunctions fo und in the elderly. Copyright (C) 2000 S. Karger AG, Basel.