Uptake of Latex and Thorotrast by Human Platelets In Vitro: Effect of Various Chemicals Demonstrating Differing Mechanisms and Metabolic Requirements

Summary In vitro platelet uptake of latex and thorotrast has been studied in the presence of a number of chemicals which inhibit metabolism and alter platelet ukrastructure. Latex uptake appears to require energy from anaerobic glycolysis and divalent cations, and is relatively easily influenced by substances which alter platelet ukrastructure. Platelet ATPases play either no role or only a minor one, and intact microtubules are unnecessary. Energy requirements for thorotrast uptake appear to be minimal or absent, divalent cations are not needed, and gross alteration of platelet ukrastructure still allows small amounts of thorotrast to gain entry into a few platelets. Platelet ATPases and intact microtubules are unnecessary for thorotrast uptake. It is concluded that latex uptake is probably by an active phagocytic process and thorotrast uptake is by a different mechanism. The relationship of increased citric acid cycle activity to degranulation and particle uptake is discussed, and it is suggested that this respiratory burst is unnecessary for either of these events, and that it is not a necessary accompaniment of platelet phagocytosis, nor specific for this process.