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Extravascular phagocytosis of proerythrocytes following 5-fluorouracil
Abstract:
Amongst the perturbations induced in mouse bone marrow by 5-fluorouracil are the retention and phagocytosis of proerythrocytes within the extravascular compartment. Reasons for the latter response have been sought using electron microscopy. Proerythrocytes undergo normal maturation after 5-fluorouracil, judged by loss of mitochondria and vesicles, but fail generally to attain a biconcave shape. Most proerythrocytes have lost their organelles before phagocytosis occurs. Quantitative light microscopy shows a rise in the number of proerythrocytes 1 d after 5-fluorouracil which is attributable to maturation of orthochromatic erythroblasts. Thereafter the population size declines concomitantly with increased engulfment and phagocytosis by macrophages, activity which is maximal on days 4-5. Extravascular loss of proerythrocytes is also observed when marrow is rendered hypocellular by x-irradiation, or hydroxyurea. It is suggested that excessive maturation of proerythrocytes in the extravascular compartment can lead to their phagocytosis.
Insights
5-fluorouracil causes mouse bone marrow proerythrocytes to mature but fail to achieve normal shape, leading to their phagocytosis by macrophages. This extravascular loss occurs due to excessive maturation.
Area of Science:
- Hematology
- Cell Biology
- Toxicology
Background:
- 5-fluorouracil (5-FU) induces perturbations in mouse bone marrow.
- Proerythrocytes are retained and phagocytosed within the extravascular compartment after 5-FU treatment.
Purpose of the Study:
- To investigate the reasons behind the phagocytosis of proerythrocytes in the bone marrow after 5-FU administration.
- To understand the maturation process and fate of proerythrocytes under cytotoxic drug influence.
Main Methods:
- Electron microscopy was used to examine proerythrocyte morphology and maturation.
- Quantitative light microscopy was employed to track proerythrocyte population dynamics over time.
- Comparative analysis with other cytotoxic agents like x-irradiation and hydroxyurea was performed.
Main Results:
- Proerythrocytes mature after 5-FU, indicated by organelle loss, but typically fail to develop a biconcave shape.
- Phagocytosis by macrophages increases significantly between days 1 and 4-5 post-5-FU, with most proerythrocytes losing organelles before engulfment.
- Extravascular loss of proerythrocytes was also observed following x-irradiation and hydroxyurea treatment.
Conclusions:
- Excessive maturation of proerythrocytes in the extravascular compartment may trigger their phagocytosis.
- The findings suggest a mechanism for erythrocyte loss independent of normal erythropoiesis, potentially contributing to hematological toxicity.