Transcription of mitochondrial and mitochondria-related nuclear genes in rabbit bladder following partial outlet obstruction

Using the rabbit model, we showed that partial outlet obstruction of the urinary bladder causes significant changes in the status and expression of the mitochondrial (mt) genetic system in bladder smooth muscle immediately after obstruction is initiated. Here we investigate quantitatively the severity of the mt genetic response to partial outlet obstruction in both short- and long-term obstructed rabbits. Based on previous functional studies, bladders with mass < 6 fold greater than control were considered compensated; bladders with mass > 6 fold that of control were considered decompensated. Analyses of DNA from compensated rabbit bladders showed that relative mt genome copy number decreased to 30% of control values. Transcript analyses for these samples showed that mt RNA levels increased 3 fold to compensate for lower template copy number. Analysis of decompensated bladders demonstrated that mt genome copy number increased to approximately 90% of control levels; mt transcripts progressively decreased in these samples by as much as 30 fold. In contrast, transcription of a mt-related nuclear gene decreased 3-9 fold in compensated bladders but increased 10-30 fold in decompensated bladders. Activity for the cytochrome oxidase complex, and for the mt enzyme citrate synthase, decreased steadily with increasing bladder hypertrophy. These data suggest that bladder dysfunction following partial outlet obstruction is mediated partly by a significant loss in mt and mt-related nuclear gene coordination.