Acute and long-term alterations in the granulocyte/macrophage progenitor cell (GM-CFC) compartment of dogs after partial-body irradiation: irradiation of the upper body with a single myeloablative dose

The acute and long-term effects of a single dose of partial-body irradiation on the granulocyte/macrophage progenitor cell compartment were studied in dogs. A myeloablative dose of 11.7 Gy (dose rate 6.5 cGy/min) was given to the upper body which contains approximately 70% of the total bone marrow mass. The lower part of the body was shielded by a lead box. In the non-irradiated bone marrow, the concentration of the GM-CFC/10(5) mononuclear cells was slightly decreased within the first 7 days and showed some fluctuations around the normal value for several weeks thereafter. In the irradiated bone marrow, virtually no GM-CFC could be detected on day 1 after exposure. Beginning on day 7, a continuous increase took place up to day 21 when the GM-CFC concentration reached between 25% (sternum) and 43% (humerus) of the initial value. No further increase took place up to day 80. Between day 120 and 380 a secondary increase was observed which reached near-normal bone marrow GM-CFC concentrations. The blood GM-CFC concentration first showed a strong depression followed by a transient increase between day 10 and 30. This coincided with GM-CFC normalization in the protected bone marrow as well as with the initial phase of regeneration in the irradiated sites. A prolonged secondary long-lasting depression between day 33 and 120 amounted to 20 to 50% of normal values. This depression was closely related to the stagnation in the GM-CFC recovery in the irradiated bone marrow sites. The GM-CFC concentration in the blood was supranormal at day 380 when the bone marrow GM-CFC had recovered. The colony stimulating activity in the serum showed an increase within the first 20 days after exposure. Within the same interval the bone marrow GM-CFC concentration experienced the strongest alterations, and was inversely related to the changes in the blood granulocyte values