The arginase activity of isolated cell nuclei.

Arginase appears to be one of the first enzymes which was studied in cell nuclei isolated on a relatively large scale by physicochemical methods. This enzyme was measured in isolated nuclei of liver cells by Behrens (1) who reported that the arginase activity per dry weight of isolated nuclei was about equal to the arginase activity of cytoplasm per dry weight in the case of mammalian liver. It was reported later from this laboratory (2) that the activity of arginase per dry weight of nuclei isolated by a different method from rat liver was 40 to 50 per cent of its activity per dry weight of whole rat liver. Recently the method of isolating nuclei of rat liver which was previously used in this laboratory has been improved, chiefly by better control of the pH and by employing a low temperature throughout the isolation procedure’ (3). It was discovered that the arginase activity of a sample of nuclei isolated from normal rat liver by the improved method was considerably higher than previously reported, and therefore it appeared desirable to reinvestigate the question of the activity of t’his enzyme in isolated liver cell nuclei. Moreover, it has recently been possible t,o extend the improved method of isolating liver cell nuclei to kidney and pancreas, and therefore it has been possible to extend the work on arginase to nuclei isolated from these two tissues. The chief results of the new investigation are (a) that the activity of arginase per dry weight of nuclei isolated from rat liver cells is slightly higher than the corresponding activity per dry weight of whole rat liver; (b) that the arginase activity of nuclei isolated from dog, lamb, rat, or chicken kidney is negligible, although arginase activity can be measured in the whole kidney of all of these species; and (~1 that the arginase activity of whole chicken liver and u-hole sheep pancreas, as well. as of nuclei isolat,ed from these tissues, is extremely low or zero, Experiments also have been carried out to determine whether the arginase of isolated liver cell nuclei is an integral part of the nucleus, or whether it is