EFFECT OF ISCHEMIA OF THE RABBIT BLADDER ON CA-MG-ACTIVATED ATPASE ACTIVITY

This investigation is concerned with the effect of Ischemia on the act ivity of Ca-Mg-stimulated ATP-ase in rabbit bladder tissue, White New Zealand male: rabbits were used for the experiments. Ischemia was prod uced by clamping of the vesical arteries. After I and 2 hours the clam ps were removed, and the animals were sacrificed 2 days later. The bla dders were removed, and the muscle acid mucosal parts of the bladders were separated. In some experiments with 2-hour Ischemia the animals w ere allowed to recover for 7 days. Homogenates were made of the muscle and mucosal tissue and separated by differential centrifugation into three parts: I) an initial particulate fraction obtained by low-speed centrifugation; 2) a supernate fraction free of mitochondria; and 3) a mitochondrial-rich fraction. ATP-ase activity was determined in the d ifferent fractions in the presence of magnesium or calcium as the acti vating ion, and the results were expressed as nmols/mg protein/minute. The following results were obtained: with the supernates, ischemia wa s found to produce a marked inhibition of enzyme activity that was lar ge and significant in muscle tissue after I hour and in mucosal tissue after 2 hours. Seven days after termination of I hour of ischemia, th e ATP-ase activity of the muscle fraction had been partially restored towards normal. Activity of ATP-ase when measured in the particulate f raction was less sensitive to the effect of ischemia; a significant di minution of enzyme activity in preparations from muscle was seen only after 2 hours of ischemia, and no inhibition was observed with mucosal tissue. ATP-ase of muscle mitochondria was severely inhibited by isch emia, and the effect of 1 hour of ischemia was not reversed 7 days aft er the insult. Mitochondria from mucosal tissue were affected to only a small extent by Ischemia. In all cases, results were similar whether magnesium or calcium was used for activation of the enzyme. (C) 1996 Wiley-Liss, Inc.