Studies have been carried out on the kinin‐forming and kinin destroying activity of rabbit macrophages obtained from the lung before and after BCG injection and from the peritoneal cavity following mineral oil injection. A similar study was carried out with L‐1210 leukaemic cells obtained from the peritoneal cavity of mice. The macrophages and leukaemic cells contain enzymes that form kinins from purified kininogen substrates at acid pH. The kinin‐forming activity is not limited to the lysosomal fraction of the cell since it is found in extra‐lysosomal compartments. Delta‐guanidovaleryl benzyl ester partially inhibits the kinin‐forming activity. Trasylol does not inhibit the kinin‐forming activity of these cells, but does inhibit the kininases of these cells. The lack of effectiveness of this agent as a general anti‐inflammatory agent is thus explained. The kininases of the normal and malignant cells are also inhibited by chloromethyl ketones such as tosyl‐lysine chloromethyl ketone (TLCK) and tosyl‐phenylalanine‐chloromethyl ketone (TPCK) as well as by copper salts. Hydroxyquinoline has no inhibitory action on these cells, indicating that they differ from the plasma kininases. Investigation of the kinins produced by enzymes in rabbit and human polymorphonuclear (PMN) cells has demonstrated the formation of a kinin that differs from bradykinin and other known mammalian kinins in its pharmacological properties, molecular weight, and amino‐terminal end group. This peptide has been named PMN‐kinin. Overall, the investigation has demonstrated the importance of white cells in contributing to the formation and destruction of “extra‐plasma” sources of kinins by enzymes which differ from plasma enzymes. Anti‐inflammatory agents may have different actions on these cell enzymes from those on plasma enzymes.

Leukokinins are peptides having 20-25 amino acids. They are formed by acid proteases contained in leukocytes, cancer cells, and ascites fluids acting on a protein substrate known as leukokininogen. The leukokinins do not contain the bradykinin sequence in their molecule. The leukokinins are extremely potent (even more so than bradykinin) in causing increased vascular permeability and hypotensive blood pressure changes. The substrate from which leukokinins are cleaved, leukokininogen is 'not' a normal constituent of plasma, but is formed in certain pathological conditions in plasma or in pathological fluids from a 'proleukokininogen'. This conversion is the limiting step in the availability of leukokinins. While all white ceils so far tested contain cathepsins D-and E-like enzymes which act as leukokininogenases (form leukokinins), the white cells do 'not' contain kallikreins and consequently do not form bradykinin. The leukokinin system may represent the system which generates fluid accumulation in pathology such as ascites of neoplastic disease, arthritis and inflammation. Strong proof of this is seen in the experiments to be described in which an inhibitor of leukokinin formation, in vitro, 'Pepstatin' retards and even prevents ascites fluid accumulation in mice in vivo.

The effect of pepstatin on the kinetics of ascitic fluid accumulation in L1210 tumor-bearing mice (DBA/2) was observed. Following inoculation of 1.5x10(6) tumor cells, untreated mice reached a peak of fluid accumulation on day 6 and remained at this level until death on day 9. A "lag" phase of 4 days occurred before fluid accumulation was seen. Pepstatin administered SC in a single dose of 80 mg/kg during the lag phase, significantly retarded fluid accumulation as compared to untreated animals. Pepstatin administered following fluid accumulation was much less effective. We concluded that pepstatin prevents fluid accumulation rather than acts as a diuretic agent. The term "ascites retardant" is suggested for the pharmacologic actions of pepstatin, since it prevents fluid accumulation without diminishing the cell count.

No abstract

No abstract