Lactate dehydrogenase activity and isoform distribution in the rat urinary bladder: effects of outlet obstruction and its removal.

The rat urinary bladder responded to infravesical obstruction by an increased weight. The weight began to increase after 3 days of obstruction. After 10 days the weight gain had become significant, but increased further with time. At 90 days the bladders weighed 12 times the initial weight. Lactate dehydrogenase (LDH) activity per unit bladder weight increased with the duration of the obstruction. The increase was significant in the 90 day group. The isoform pattern of LDH was determined. For the control group the M3H form was dominant, with M4 second; M4 became the dominant isoform after 3 days of obstruction. The relative amount of M4 had increased by 80% after 90 days. In one group, which was first obstructed for 10 days and then had the obstruction removed for 4 weeks, bladder weight and LDH isoform pattern were normal. We suggest that the changes in isoform pattern in the obstructed bladder reflect a metabolic adaptation to the prolonged voiding time and the increased detrusor pressure, with a consequently compromised oxygen supply, and that the changes are reversible if the outlet conditions are normalized.