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Phagocytosis of liposomes by human platelets

Male, Roxanne and Vannier, Wilton E. and Baldeschwieler, John D. (1992) Phagocytosis of liposomes by human platelets. Proceedings of the National Academy of Sciences of the United States of America, 89 (19). pp. 9191-9195. ISSN 0027-8424. PMCID PMC50091. doi:10.1073/pnas.89.19.9191.

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We have shown that platelets are capable of phagocytosing liposomes rather than simply sequestering particles as previously postulated. Incubation of human platelets with small neutral unilamellar liposomes (almost-equal-to 74 nm) resulted in uptake of the liposomes and retention of the lipid with rapid release of the aqueous-phase components. The lipid label [H-3]-cholesterylhexadecyl ether and water-soluble [H-3]inulin were used to study the fate of the liposome components. Uptake of liposomes was proportional to the number of liposomes added and to the incubation time. Approximately 250 liposomes per platelet were taken up within a 5-hr incubation period. Uptake of the liposomes occurred through the open-channel system, as evidenced by thin-section electron microscopy, and was followed by accumulation and degradation in acid- and esterase-containing vesicles, as determined by changes in fluorescence of the pH-sensitive probe, pyranine (1-hydroxypyrene-3,6,8-trisulfonic acid), and hydrolysis of the cholesteryl [C-14]oleate membrane marker. Uptake was inhibited by the addition of EDTA, cytochalasin B, or 2,4-dinitrophenol and iodoacetate to the medium. Results from the serotonin release assay, microaggregation assay, fluorescein diacetate membrane integrity assay, and electron microscopy indicate that neither the conditions for loading nor phagocytosis of liposomes significantly alter platelet function or morphology.

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Additional Information:© 1992 by the National Academy of Sciences. Contributed by John D. Baldeschwieler, May 15, 1992. We are indebted to Dr. Dudley Moon (Albany College of Pharmacy) and Dr. Pramod Lad and his staff (Kaiser Regional Research Laboratory, Los Angeles) for their advice during the course of the work. We thank Dr. G. L. Scherphof for suggesting the use of the cholesteryl [14C]oleate hydrolysis method. Funding for this work was provided by Army Research Office Grant DAAL-03-87-K-0044 and the Caltech Consortium in Chemistry and Chemical Engineering (founding members: E.I. du Pont de Nemours and Company, Inc., Eastman Kodak Company, Minnesota Mining and Manufacturing Company, Shell Oil Company Foundation). The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.
Funding AgencyGrant Number
Army Research Office (ARO)DAAL-03-87-K-0044
Caltech Consortium in Chemistry and Chemical EngineeringUNSPECIFIED
Issue or Number:19
PubMed Central ID:PMC50091
Record Number:CaltechAUTHORS:MALpnas92
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:1451
Deposited By: Tony Diaz
Deposited On:19 Jan 2006
Last Modified:08 Nov 2021 19:10

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