Evidence for a major role of plasma lipoproteins as hematoporphyrin carriers in vivo.

Hematoporphyrin (5 mg/ml), administered intravenously to tumor-bearing patients, becomes associated with different serum proteins, including lipoproteins (mainly HDL), globulin and albumin. No residual porphyrin is bound to the two latter classes of proteins after 48 h, whereas the complexation with the lipoproteins appears to be particularly stable probably owing to the hydrophobic nature of hematoporphyrin. The late persistence of hematoporphyrin in serum is due to the binding to the VLDL fraction with special regard to its cholesterol moiety. The importance of hematoporphyrin transport by lipoproteins for the photodynamic therapy of tumors is briefly discussed.