Morphological and Biochemical Study on the Processes of Apoptosis Induced by Radiation

ABSTRACT

Transglutaminase(TGase) is a calcium dependent enzyme that catalyse and acyl transfer reaction forming epsilon-(gamma-glutamyl)-lysine cross linkage. the major known effect of TGase is its important role in the programmed cell death manifested in the granular layer of the skin and acidophilic bodies in the viral hepatitis and neoplastic processes. The enzyme activity, immunohistochemical reaction using polyclonal antibodies against cytosolic TGase C, light and electron microscopic studies and TdT staining of the transplanted fibrosarcoma cells in C3H mouse with radiation therapy were done. The presence of TGase was detected immunohistochemically by avidin-biotin peroxidase complex (ABC) method Apoptosis were significantly induced after irradiation dependent with time factors and irradiation doses, resulted in marked and confluent tumor cell loss. Highest activity of the cytosolic form of TGase was noted at 24 hours and decrease after then while membrane bounded form of the TGase showed no significant changes. Immunohistochemical staining revealed strong positive reaction in the sarcoma cells in diffuse fasion and around the necrotic foci in the cytoplasm. Terminal dideoxynucleotidyl transferase(TdT) staining revealed increasing numbers of apotptic cells from two hours after irradiation. In the mechanism of decreasing tumor size and cell death in radiation therapy, apoptosis plays an important role and during that process transglutaminse might do some irreversible cross-linking effects of cytoplasmic proteins causing cell death in part.