Partial obstruction of the rat urinary bladder: effects on mitochondria and mitochondrial glucose metabolism in detrusor smooth muscle cells.

The aim of the present study was to measure mitochondrial function in the obstructed rat bladder, which does not seem to have impaired contractility in vivo. The animals were unoperated control rats and rats with a 12-day partial urinary outlet obstruction. The obstruction increased bladder weight 3-fold. The relative volume (3.5%) in the detrusor smooth muscle cells composed of mitochondria was unaffected by obstruction. Obstruction did not affect malate dehydrogenase and citrate synthase activity when expressed relative to unit bladder weight. There was, however, a significant decrease in enzyme activity when expressed relative to protein content. This was due to an increased relative protein content in the obstructed bladders. Total enzyme activities per bladder were increased. Oxygen consumption rates in maximally activated intact control and obstructed preparations in other studies corresponded to a citrate synthase (rate-limiting enzyme) activity only 10% of the maximal enzyme activity found in the present study. We conclude that there is a considerable safety margin in mitochondrial function in intact rat detrusor muscle cells, and that detrusor smooth muscle cells can hypertrophy without any impaired mitochondrial function.