In vivo metabolism of platelet-activating-factor (1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) by the protozoan Tetrahymena pyriformis.

The metabolism of exogenous platelet-activating-factor was studied in the protozoan Tetrahymena pyriformis in vivo. When the cells are exposed to 1.10(-6) M PAF, the molecule is rapidly metabolized to 1-O-alkyl-2-acyl(long chain)-GPC, a major component of the protozoan membranes. The appearance of lyso-PAF from the first minutes even in low levels provides evidence that deacetylation is an intermediate step. After incubation for 30 min, transformation to aminoethyl phosphonolipids is also observed. The fate of PAF in concentrations 1.5.10(-11) M or 1.10(-8) M PAF, was the same. An amount of PAF depending on the external PAF concentration remained intact in the cell even after 1 h incubation. Our results suggest that the easily cultured protozoan can be a useful model for studying PAF's metabolism.