Effect of partial outlet obstruction on 14C-adenine incorporation in the rabbit urinary bladder

Bladder outlet obstruction induces severe changes in urinary bladder function and metabolism. These changes are characterized by significant reductions in the ability of the in vitro whole bladder to generate pressure and to empty. Metabolically, partial outlet obstruction induces a shift from oxidative to anaerobic metabolism. The decreased oxidative metabolism is mediated in part by significant decreases in mitochondrial substrate metabolism, which in turn is correlated with decreased activity of 2 important mitochondrial enzymes: citrate synthase and malate dehydrogenase. The present study was designed to evaluate mitochondrial function by studying the incorporation of 14C-adenine into high-energy phosphates (ATP, AMP, and ADP). Mild partial outlet obstructions were created by surgically placing silk ligatures loosely around the bladder neck. The results of these studies demonstrate that after 60 min incubation in oxygenated medium containing glucose + 1uCi14C-adenine, 1) There was no significant differences in the total AMP, ADP, and ATP concentrations measured in bladders taken from controls, 7- and 14-day obstructed rabbits; 2) there was no effect of obstruction on either the concentration of 14C-AMP in the tissue or in the ratio of hot to cold AMP; and 3) there was a 50% decrease in the concentration of 14C-ADP and a 70% decrease in the concentration of 14C-ATP in the bladder smooth muscle obtained from obstructed tissue (from both 7- and 14-day obstructions) compared to concentration in the control bladder smooth muscle. These results confirm the previous finding that obstruction did not reduce the rate of incorporation of adenine to AMP within the obstructed bladder smooth muscle and extends these studies to identify a significant reduction in the synthesis of both ADP and ATP. These results support the hypothesis that partial outlet obstruction induce a major dysfunction in mitochondrial function, both in the ability to oxidize substrates and in the ability to generate ATP.