Analysis of phospholipid transfer during HDL binding to platelets using a fluorescent analog of phosphatidylcholine.

Electron microscopic examination of the interaction of gold labelled HDL with platelets indicates that the internalized lipoprotein becomes closely associated with surface connected canaliculae and endocytic vacuoles. At the same time granule centralization occurs. Using fluorescent derivatives of naturally occurring lipids we have further investigated lipid exchange between HDL and platelets. Analogs of phosphatidylcholine containing fluorescent fatty acids are rapidly transferred from the lipoproteins to the cells and remain at the plasma membrane as long as they are kept at 4 degrees C. However when the platelets are warmed to 37 degrees C, a rapid degradation of the fluorescent lipids occurs, generating fluorescent diacylglycerol as a consequence of the activation of platelet enzymes.