Carnosine as a stimulator of cytotoxic and phagocytic function of peritoneal macrophages

: Biochemical changes in peritoneal macrophages and their relatedness to the cytostatic and phagocytotic function in C3HA mice injected with a single intraperitoneal dose of 0.45 mM carnosine and 4-methyluracil or stimulated with peptone have been studied. During the first 24 hours after injection both carnosine and 4-methyluracil increase the activity of adenosine deaminase and purine nucleoside phosphorylase, the key enzymes of purine catabolism which is the main source of O2-. radicals in macrophages. In carnosine-stimulated macrophages the activity of membrane 5'-AMP nucleotidase decreases on days 1-3 after injection which points to alleviation of adenosine-induced inhibition as well as to macrophage activation. Carnosine increases the cytostatic and phagocytotic activities of macrophage coupled to O2-. production. The mechanism of the stimulating effect of carnosine on macrophages seems to consist in the dipeptide interaction with specific receptors localized on the plasma membrane of macrophagal cells.