What Is Radiosensitivity?

It refers to the speed of death, injury or other effects after the body or cells, tissues, organs receive ionizing radiation under the same radiation conditions. There is a certain relationship between the radiation sensitivity of biological systems and the content of DNA. The higher the degree of biological evolution, the more complex the organism's tissue structure, and the higher its radiation sensitivity.

Generally, the mortality of the body or cells after a certain dose of radiation or the value of LD ₅₀ is used as a criterion for judging radiosensitivity, or a certain morphological or functional change is used as an index of radiosensitivity of a tissue; in a cell population D ₀ , D _g , D _{37 are} also used as indicators for analyzing radiosensitivity.

In phylogeny, the general trend is that radiosensitivity increases as the line evolves. In terms of individual development, radiosensitivity is higher in the embryonic stage, and it is more sensitive in young and old age than in adulthood. The radiosensitivity of different tissues and organs is generally directly proportional to the intensity of their cell division activities and inversely proportional to the degree of their cell differentiation.

At the subcellular and molecular levels, the radiosensitivity of the nucleus is higher than that of the cytoplasm. The relative sensitivity of different target molecules in the cell is:

DNA> mRNA> RNA> tRNA> protein ^[1]

The radiation sensitivity is shown below

There are significant differences in the radiosensitivity of different tissues, organs, cells, and different stages of fertility and physiological status. Early multicellular organisms (such as all organs of the fetus) and organs with strong cell divisions (such as germ cells, hematopoietic tissue, intestinal epithelium, immune system, cancer cells) are highly radiation-sensitive, and like adults, most of the nerves and brain Tissues that divide slowly, such as muscle, liver, mature blood cells (with the exception of lymphocytes), show antiradiation. In general, dividing cells have the highest sensitivity. However, the sensitivity varies greatly depending on the species and genetic characteristics. In the case of mammalian culture cells, from the end of the G1 phase to the beginning of the S phase, both are sensitive to X-rays and ultraviolet rays, while in the G2 phase, they are only highly sensitive to X-rays, but they are sensitive to ultraviolet rays. Appears as radioactive (radiation resistance).