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 contr actility in vivo. The animals were unoperated control rats and rats wi th a 12-day partial urinary outlet obstruction. The obstruction increa sed bladder weight 3-fold. The relative volume (3.5%) in the detrusor smooth muscle cells composed of mitochondria was unaffected by obstruc tion. Obstruction did not affect malate dehydrogenase and citrate synt hase activity when expressed relative to unit bladder weight. There wa s, however, a significant decrease in enzyme activity when expressed r elative to protein content. This was due to an increased relative prot ein content in the obstructed bladders. Total enzyme activities per bl adder were increased. Oxygen consumption rates in maximally activated intact control and obstructed preparations in other studies correspond ed to a citrate synthase (rate-limiting enzyme) activity only 10% of t he maximal enzyme activity found in the present study. We conclude tha t there is a considerable safety margin in mitochondrial function in i ntact rat detrusor muscle cells, and that detrusor smooth muscle cells can hypertrophy without any impaired mitochondrial function. (C) 1997 Wiley-Liss, Inc.