Translocation of exogenous platelet-activating factor and its lyso-compound through plasma membranes is a rate-limiting step for their metabolic conversions into alkylacylglycerophosphocholines in rabbit platelets and guinea-pig leukocytes.
Platelets and leukocytes are known to degrade platelet-activating factor (PAF), a potential mediator of inflammation, to its lyso-derivative (lyso-PAF) and then convert this to 1-O-alkyl-2-acyl-sn-glycero-3-phosphocholines. However, little is known about the mechanism of internalization of PAF and lyso-PAF, which is a prerequisite for their metabolism within the cells. In this work, the internalization of PAF and lyso-PAF by rabbit platelet and guinea-pig leukocyte plasma-membranes were examined by the washing method with bovine serum albumin. The rates of translocation of PAF and lyso-PAF across guinea-pig plasma membranes were significantly higher than those across rabbit platelets. In these cells, the translocation of PAF was found to be accelerated indirectly by activation of PAF receptors by a small portion of added PAF. Results suggest that a temperature-dependent diffusion process is involved in the internalization of these phospholipids. In both rabbit platelets and guinea-pig leukocytes, the translocation of PAF and lyso-PAF through the plasma membranes was shown to be rate-limiting for the metabolic conversion of these compounds to 1-O-alkyl-2-acyl-sn-glycero-3-phosphocholine.
Tokumura
A
A
Faculty of Pharmaceutical Sciences, University of Tokushima, Japan.
Tsutsumi
T
T
Yoshida
J
J
Tsukatani
H
H
D000818:Animals; D001692:Biological Transport; D001792:Blood Platelets / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D006168:Guinea Pigs; D007700:Kinetics; D007962:Leukocytes / Q000378:metabolism*; D008297:Male; D009504:Neutrophils / Q000378:metabolism; D010743:Phospholipids / Q000378:metabolism; D010972:Platelet Activating Factor / Q000031:analogs & derivatives* / Q000378:metabolism*; D011817:Rabbits
C036761:1-alkyl-2-acyl-sn-glycero-3-phosphocholine; D010743:Phospholipids; D010972:Platelet Activating Factor