Effect Of Fractionated And Single Doses Gamma Irradiation On Certain Mammalian Organs

The present work aims to study the effect of fractionated and single dose whole body gamma irradiation on the liver, spleen and intestine of albino rats. 30 Male albino rats (100-120g) were used as experimental animals, they were divided into three groups: The first group consists of 10 rats served as control group (non irradiated), the second group (10 rats) were subjected to a single dose of irradiation (5Gy) and the third group (10 rats) were subjected to gamma of irradiation (5Gy) delivered at 5 successive exposures daily. Histological results showed serious histopathological disorders in the liver, spleen and intestine after exposure to the single dose of gamma irradiation (5Gy), manifested by inflammation and infiltration with mononuclear cells, haemorrhage, dilatation, congestion and widening of blood vessels and necrosis of cells with pyknotic nuclei. Exposure of rats to fractionated doses of whole body gamma irradiation (1Gy) up to 5Gy resulted in less severe histopathological disorders in liver, spleen and small intestine (jejunum), This indicates the beneficial use of fractionated doses in planning for radiotherapy in cancer patients, thus reducing the serious histopathological changes of radiation on the human tissues. Introduction Life on earth has evolved in the presence of ionizing radiation from several sources. In addition to natural background radiation, humans are exposed from man made sources. The largest component of man-made background radiation relates to exposures associated with medical diagnosis and treatment (Kissan and Anderson 1985). Exposure to radiation causes injury to blood vessels provoking anoxia of tissues with degeneration and necrosis (Jirtle et al., 1990) Many of the damaging effects of ionizing radiations are mediated by free radicals. Superoxide (O) and hydroxyl radical (OH) attack the polyunsaturated fatty acids of cell membrane phospholipids resulting in severe damage to cellular membrane organelles and their associated enzymes (Halliwell and Gutteridge, 1989). The cell membrane permeability is disturbed following irradiation as exhibited by changes in tissue ionic contents of Na and K (Hassan and Osman, 1996) The biological effect of radiation correlates with the given doses (Fowler, 1994). The most important target in living cells is DNA. Ionizing radiation may directly damage DNA (direct target theory), but more often it indirectly damages DNA by inducing the formation of free radicals, particularly those that form the radiolysis of water (indirect target theory). Other cell molecules that may also be direct or indirect targets of radiant injury include lipids in cell membranes and proteins that function as critical enzymes. The transfer of energy to a target atom or molecules from the incident source of radiant energy occurs within micro fractions of a second, yet its biological effect may become apparent for minutes or, if the effect is on DNA, even decades (Kumar et al., 2003). The objective of this work was to evaluate the ameliorative effect of the single or fractionated irradiation doses when planning a radiotherapy programme for medical practice aiming to reduce the