Background
The aim of the present study was to investigate the effect of different gamma-radiation doses on hematological and dimensional properties of rat blood in vivo in an attempt to understand the toxicity and the potential role of gamma-irradiation as a therapeutic tool.

Methods
60 healthy male Wistar-Kyoto rats were used in this study. Animals were randomly divided into five groups, 4 gamma-irradiated rat groups [(The 1st group irradiated with five gamma radiation; the 2nd group irradiated with 25Gy; the 3rd group irradiated with 50 Gy); the 4th group irradiated with 100Gy] and one control group. Then different hematological parameters measured using the standard hematological techniques.

Results
After irradiating the 4 gamma-irradiated rat groups with different gamma radiation doses, a significant decrease in white blood cells (WBCs) count, lymphocytes (LYM), red blood cells (RBCs) count, hemoglobin (HGB), and hematocrit (HCT) was observed compared with the control. While a significant increase in monocytes (MON), neutrophils (NEU), basophils (BAS), eosinophils (EOS), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH) and mean corpuscular hemoglobin concentration (MCHC), red distribution width (%RDW) was observed. A non-significant decrease in platelets (PLTs) count observed with gamma radiation doses compared with the control.

Conclusions
The organism becomes susceptible to any infection that may point toward a bone marrow problem as well as production of an infection or toxic reactions or chemicals. A low RBCs count or low HGB or HCT may suggest anemia. The cessation of erythrocytes production in the bone marrow. The increase in RBCs size indicates changes in morphology and deformability of RBCs confirmed by slightly increase in the red cell distribution width.