This work aimed to study the biochemical, histopathological and histochemical changes in the testes of
male albino rats post exposure to 4 Gy of gamma radiation and the possible radioprotective role of Aphanizomenon flos-aquae (AFA). Aphanizomenon flos-aquae (AFA) is a blue-green microalgal species which has antioxidant properties. The current experiment was carried out on 48 adult male albino rats (Rattus rattus). Rats were randomly and equally categorized into four groups: 1) Group C: control rats left without treatment; 2) Group R: rats were exposed to 4Gy of gamma-radiation as a single dose; 3)
Group AFA: rats were terated orally with 94.5mg/kg body weight/ day AFA for 3 weeks and 4) Group AFA+R: rats were administrated AFA for a period of one week before and three weeks after irradiation. Results obtained in the present study showed that exposed rats showed a significant increase in MDA in the testes, but decreased testosterone level was detected versus the control. Many histopathological lesions were observed in the testes tissue such as disturbed spermatogenic layers with vacuolated spermatogenic cells, presence of polynucleated cells, absence of mature sperms, oedema in the interstitial spaces, congested testicular arteries with thickened, dilated and corrugated walls of them, they also contained hemolysed blood cells with highly reduced, atrophied and distorted Leydig cells in the interstitial spaces. Irradiated groups showed highly increased collagen fibres under the testicular capsule, basement membranes, Leydig cells and around the blood vessels with signs of fibrosis in the capsule and some seminiferous tubules In addition, irradiated group induced a significant increase in amyloid - protein, while a significant decrease in PAS+ve materials, total protein and total DNA content was detected. AFA administration ameliorated the damaging effects of testes of radiation exposed rats. Conclusion: according to the results obtained in the current study using Aphanizomenon flos- aquae as a natural agent showed a strong radioprotective role. Key words. Gamma rays, ionizing radiation, Aphanizomenon flos-aquae (AFA), testes, rats.