Porphyrin-lipoprotein association as a factor in porphyrin localization.

Systemic administration of the tumor-localizing product hematoporphyrin derivative (HPD) to mice bearing the Lewis-Lung tumor leads to an initial distribution of porphyrins among plasma lipoproteins and albumin. The more hydrophobic components of HPD (including the tumor-localizing fraction) preferentially bind to plasma low density lipoprotein (LDL) and high density lipoprotein (HDL). After 48 h, the remaining plasma porphyrins are mainly bound to HDL. The distribution pattern of HPD is correlated with the relative numbers of LDL receptors in different tissues.