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The content of adenosine 3',5'-monophosphate in human mononuclear leukocytes was enhanced 3-5-times by venoms obtained from African toad (Bufo africanus), American toad (Bufo americanus), Colorado river toad (Bufo arenarum) and Marine toad (Bufo marinus) at 25 micrograms/ml for 5 min of incubation at 37 degrees C. The maximum stimulation was observed after 1-5 min of incubation. The half-maximal stimulation was observed at 0.1 micrograms/ml venom obtained from Colorado river toad (Bufo arenarum). The increased content of adenosine 3',5'-monophosphate in the mononuclear leukocytes persisted without significant change for at least 30 min of incubation at 37 degrees C.

Contact of human polymorphonuclear leukocytes with latex or zymosan particles resulted in inhibition of incorporation of 14C-labeled amino acids into protein in the phagocytosing cells. The surface-active agents, concanavalin A and digitonin, exerted the same inhibitory activity on 14C-labeled amino acid incorporation into protein in human granulocytes. The inhibition of 14C label incorporation was dose dependent and the half-maximal effect per 10(7) cells was found at 0.8 mg of latex (0.79 micrometer in diameter), 0.25 mg of serum-coated zymosan and 35 microgram of digitonin/ml of the incubation medium. Amino acid transport (14C-labeled amino acids or amino[14C]isobutyrate) was the same in the resting and phagocytosing granulocytes. These results suggest that the incorporation of 14C-labeled amino acids into protein in human granulocytes is in some way connected to alteration in the cell plasma membrane.