Effect of heme on vascular permeability.

Permeability was analyzed by gamma camera imaging and biodistribution of ^99mTc-labeled liposomes in C57Bl/6 mice. (A) Scintigraphic image of mice 4 hours after injection with^99mTc-labeled liposomes in the presence of either PBS or heme. A clear shift of radiolabeled liposomes from the heart in control mice to the abdominal region in heme-treated mice can be observed. (B) Effect of heme on the biodistribution of ^99mTc-labeled liposomes in mice 24 hours after injection. Animals treated with PBS and heme are represented by white bars and black bars, respectively. Results are expressed as percentage of injected dose per organ (% ID). All values are indicated as mean ± SD of 5 mice. There is a significant increase in the accumulation of liposomes in the pancreas, liver (P < .00005), spleen, kidneys, intestines, brain (P < .01), and femur (P < .05) of the heme-treated animals compared to the PBS-treated animals. (C) Biodistribution of ^99mTc-labeled liposomes in mice 24 hours after injection, corrected for weight. Animals treated with PBS and heme are represented by white bars and black bars, respectively. Results are expressed as a percentage of injected dose per 0.1 g tissue (% ID/0.1 g). All values are indicated as mean ± SD of 5 mice. There is a significant increase in the accumulation of liposomes in the pancreas (P < .0005), spleen (P < .01), liver, and intestines (P < .05) of the heme-treated animals compared to the PBS-treated animals.