Accumulation of phospholipase A1 in tissue fluid of rabbits infected with Trypanosoma brucei.

Samples of tissue fluid were obtained from plastic cages implanted subcutaneously in rabbits. A phospholipase A1 similar to that found in Trypanosoma brucei appeared in the tissue fluid about seven days after infection with this parasite, increasing with parasite burden, and reaching levels of more than 5 nmol phosphatidylcholine hydrolysed per min per ml tissue fluid. The large amount of phospholipase A1 found free in the tissue fluid appeared to be of trypanosomal origin and was either secreted by living parasites or released from dying organisms. Phospholipase A1 was detectable in blood plasma from the infected rabbits, but at a level considerably lower than in the tissue fluid. An inhibitor of the phospholipase was present in the plasma after the first two week of infection which may be partly responsible for this lower level.