Acute biochemical and functional alterations in the partially obstructed rabbit urinary bladder.

Rapid structural and functional alterations have been noted in several models of partial outlet obstruction. To better characterize the rapid progression of alterations, the partially obstructed urinary bladders of mature NZW male rabbits were studied at 1, 3, 5, 7 and 14 days of outlet obstruction with respect to muscarinic receptor density, DNA, RNA, lipid and hydroxyproline content. Functional characteristics were assessed by measuring the in vitro response of the whole bladder to cholinergic and field stimulation. Wet weight increased eight-fold by day 7, decreasing to four-fold at day 14. Receptor density decreased by 50% by day 1 and remained low throughout. Although DNA concentration varied only slightly from controls, RNA increased four-fold by day 7. Hydroxyproline concentration per mg. tissue decreased in the obstructed bladder, yet total hydroxyproline content of the obstructed bladder significantly increased. Total lipids increased significantly during day 3 through 7 and decreased by day 14. Cystometry revealed a large capacity low pressure system at day 1 which rapidly changed to a low compliance system of lesser volume by day 14. Bladder emptying was significantly impaired in all obstructed specimens. Additionally, electrical field stimulation was significantly less effective than cholinergic stimulation in effecting bladder emptying. The above findings suggest that rapid changes in biochemical parameters occur during the early stage of acute obstruction which may in part be secondary to metabolic or inflammatory alterations in the detrusor. It additionally suggests that the myogenic alterations in partial outlet obstruction are rapid and partially adaptive, while neurogenic alterations appear degenerative and display a lesser degree of short term adaptation.