Partial outlet obstruction of the rabbit urinary bladder induces selective protein oxidation

Aims: Oxidation of proteins is presumed to contribute to contractile dysfunction associated with partial outlet obstruction (PBOO) of the urinary bladder. The objective of this study was to determine the acute and chronic effects of PBOO on protein oxidation in urinary bladder detrusor smooth muscle (DSM) and mucosa, and to correlate these findings with in vitro contractile function. Methods: Urinary bladders of New Zealand White (NZW) rabbits were obstructed for 1, 3, 7 and 14 days. Proteins were extracted from the bladder tissues and protein carbonyl formation was assessed using immunoblot assays. In vitro contractile response to field stimulation (32 Hz) and carbachol was evaluated in whole bladder strips at the same time points. Results: Significant elevations in oxidation of DSM proteins were observed in the MW range of 29-65 kDa after 3 days and 14 days of obstruction. No changes in the oxidative status of mucosal proteins were detected as a result of short or long term obstruction. The intermediate filament protein, desmin (53-55 kDa) was detected in obstructed DSM samples in the same MW range as oxidized proteins. A significant decrease in contractile response to field stimulation and carbachol was observed after 1 day and 3-days respectively, and continued to deteriorate through 14 days. Conclusion: The increase in protein oxidation at 14-days of obstruction correlates with impaired bladder contractility, suggesting that oxidatively modified proteins may contribute to the contractile and biochemical dysfunction associated with PBOO.