Tissue fractionation studies. 10. Influence of ischaemia on the state of some bound enzymes in rat liver

Abstract

The activity and state of a number of bound enzymes have been followed in a rat-liver lobe rendered completely ischemic by ligation of the vascular pedicle. The unligated part of the same liver was used as an internal control. The enzymic determinations were performed on the homogenized tissue samples and on high-speed supernatants from these homogenates. The earliest change observed after complete ischemia was a progressive release of the lysosomal hydrolases, acid phosphatase, [beta]-glucuronidase, cathepsin, acid ribonuclease and acid deoxyribonuclease. This release reached a plateau, corresponding to the rupture of about 80%, of the lysosomes, in the space of 3-4 hr. Whether the phenomenon actually occurred within the cells or only upon homogenization is not known, but the former interpretation is favored as providing a satisfactory explanation of how autolytic processes are initiated in necrotizing cells. Changes in total enzymic activities were as follows: cytochrome oxidase lost about 9/10 of its activity in 6-8 hr. and then remained constant; glucose 6-phosphatase did the same in 10-12 hr.; acid phosphatase remained unchanged during the first day and then slowly decreased to about half its value during the 2d day; cathepsin and the 2 acid nucleases suffered a fairly rapid partial inactivation, reaching 50-60% of their activity after about 8 hr., and then decreased very slowly; [beta]-glucuronidase was unaffected for 6 hr. and then increased by about 40% during the next 12 hr. and remained elevated. All 5 lysosomal hydrolases were still present at half or more their initial concentration 48 hr. after the blood supply had been cut off, thus showing a survival time consistent with their assiimed role in autolysis. From studies on isolated liver slices and on particles it appears that the ischemic release of lysosomal hydrolases may be due to an anoxic change in the intracellular environment of the particles, possibly a lowering of the pH.