DISCUSSION
Previous manometric studies by Berk and Nelson (1960) indicated that succinoxidase activity of mouse monocytes was depressed by a few micrograms of a Pseudomonas polysaccharide (piromen) which contained traces of a lipidnucleic acid moeity. Cytochrome oxidase was relatively unaffected. Further studies (unpublished) indicated that a soluble and a particulate component of disrupted P. aeruginosa inhibited succinoxidase activity of mouse monocytes to a greater extent than did intact bacteria. Similar inhibitory effects on succinoxidase activity of monocytes or spleen and liver homogenates could not be demonstrated with commercially available bacterial lipopolysaccharides (unpublished results). Whereas previous studies (Berk et al, 1960b) indicated that the respiratory enzymes of mouse monocytes were relatively weak, with large numbers of cells required for activity, the studies reported here indicate that these cells are rich in nonoxidative enzymes. Acid phosphatase, alkaline phosphatase and beta glucuronidase were all present in mouse monocytes. In addition, amylase and arylsulfatase have also been found in these cells (unpublished data). Several. investigators (Cohn and Hirsch, 1960a, b; Cram and Rossiter, 1949; Fishman, 1955; Haight and Rossiter, 1946; Roche, 1931) have also shown phosphatases and beta glucuronidase in circulating leucocytes and rabbit polymorphonuclear cells. Using human cells, Haight and Rossiter (1946) found alkaline phosphatase chiefly in polymorphonuclear leucocytes and acid phosphatase mainly in lymphocytes. Roche (1931) demonstrated alkaline phosphatase activity in both granulocytes and lymphocytes from the buffy coat of rabbit and guinea pig blood. Recently, Cohn and Hirsch (1960a, b) reported the presence of hydrolases in rabbit polymorphonuclear leucocytes.
The study of these mouse enzymes was aided by the fact that fewer cells were required than for oxidative studies. Furthermore, despite the fact that some substances stimulated enzyme activity, the enzymes were both stable and active without the use of cofactor supplements. On the basis of cell numbers, beta glucuronidase was especially active in comparison to the 2 phosphatases or to succinoxidase. Activity could be detected with as little as 5 X 104 cells per ml, whereas studies with phosphatases and oxidases required 5 X 106 and 5 X 108 cells per ml, respectively. Attempts to increase the rate of beta glucuronidase activity by using possible activators yielded a variety of results. The influence of bovine serum albumin and other substances on this enzyme for other mammalian tissue preparations has been reported (Bernfeld et al, 1954). Heparin, routinely used to prevent clumping of cells, had no appreciable effect on beta glucuronidase activity in monocytes, though Becker and Friedenwald (1949) found it inhibitory to this enzyme in liver preparations. Unlike bovine serum albumin, sodium chloride and hyaluronic acid, trace amounts of citrate did not stimulate beta glucuronidase. Other investigators (Karunairatnam and Levvy, 1949) have used mouse liver preparations and also found this to be true.