BINDING-PROPERTIES OF INDOCYANINE GREEN IN HUMAN BLOOD

PURPOSE. Binding properties of indocyanine green (ICG) to human plasma proteins were identified using electrophoresis and a fundus video sys tem. METHODS. Blood samples were obtained from three healthy volunteer s after intravenous administration of ICG. The resulting plasma sample s were fractionated by agarose gel immunoelectrophoresis and polyacryl amide gel DISC electrophoresis. In the former, antisera, anti-apolipop rotein (Apo)-A, and anti-Apo-B antibodies were used to identify all cl asses of plasma proteins, high-density lipoprotein (HDL), and low-dens ity lipoprotein (LDL), respectively. In the latter method, plasma samp les could be separated into chylomicron, very low-density lipoprotein, LDL, and HDL. The electrophoretic pattern obtained by each method was observed with an ICG fundus video system. Furthermore, we studied the affinity of ICG for lipids that were common molecular components of H DL and LDL. Four kinds of ICG solutions mixed with phospholipid, free cholesterol, esterified cholesterol, and triacylglycerol were observed with the ICG fundus video system. RESULTS. Both electrophoretic studi es showed that ICG bound intensely to HDL and moderately to LDL, and o nly the solution with phospholipid fluoresced brightly when observed w ith the ICG fundus video system. CONCLUSIONS. These findings indicated low vascular or tissue permeability of ICG, which is caused by the la rger molecular size of HDL and LDL. Also noted was that the ICG fluore scence observed in the angiogram may he equivalent to the hemodynamics of HDL alone or in combination with LDL in the bloodstream. This bioc hemical consideration may be a basis for the further understanding of ICG angiography.