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Pathologic changes in the lungs of mice following injection of human albumin microspheres
Abstract:
Mice injected with 131I-human albumin microspheres equivalent to 10-20 or 200 human doses were sequentially killed over a 12-day period. About 90% of the microspheres initially lodged in the precapillary arterioles and capillaries of the lungs. Their pulmonary clearance was essentially complete after 3 days. Occlusion of the vessels always led to focal hyperemia of the surrounding tissue and to slight hemorrhage into the alveoli. This was followed, though less frequently, by perivascular nodular inflammtion. Hemorrhagic infarcts were quite uncommon and occurred only after the massive doses. Some emboli underwent organization, but most were resolved. Circulatory disturbances and perivascular inflammation receded in about 1 week and seldom led to obliteration of the involved vessels. Hemorrhagic infarcts were converted into minute scars. Twelve days after injection of microspheres in massive doses, the only findings were post-inarct scars and obliterated vessels, which were sparse and difficult to detect. The lower doses of microspheres did not leave any detectable residues.
Insights
Radioactive albumin microspheres injected into mice primarily lodge in lung capillaries. While causing temporary inflammation and hemorrhage, these microspheres are largely cleared or resolved, leaving minimal residue.
Area of Science:
- Radiology
- Pathology
- Pulmonary Medicine
Background:
- Iodine-131 (131I)-labeled human albumin microspheres are used in medical imaging and therapy.
- Understanding the biodistribution and tissue response to these microspheres is crucial for safety and efficacy.
Purpose of the Study:
- To investigate the fate and tissue effects of 131I-human albumin microspheres in mice following pulmonary arterial injection.
- To assess the dose-dependent pathological changes and clearance rates.
Main Methods:
- Mice were injected with varying doses of 131I-human albumin microspheres.
- Animals were sequentially euthanized over a 12-day period for histological examination.
- Microsphere distribution, tissue reactions, and clearance were analyzed.
Main Results:
- Approximately 90% of microspheres lodged in pulmonary precapillary arterioles and capillaries.
- Pulmonary clearance was nearly complete within 3 days.
- Observed effects included hyperemia, alveolar hemorrhage, and occasional perivascular inflammation; hemorrhagic infarcts were rare and associated with massive doses.
- By day 12, massive dose injections resulted in sparse post-infarct scars and obliterated vessels; lower doses left no detectable residues.
Conclusions:
- Pulmonary embolization with 131I-human albumin microspheres leads to transient vascular occlusion and inflammatory responses.
- The observed pathological changes are generally reversible and dose-dependent.
- Microspheres are effectively cleared or resolved, with minimal long-term tissue damage, especially at lower doses.