RADIOSENSITIVITY AND APOPTOSIS OF SPERMATOGONIA

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The purpose of this study is to identify the mode of radiation-induced cell death in the tesitis and other tissue.Male C57BL or BALB/cA Jcl-nu mice were irradiated with single doses of 0.5, 2.5 or 5.0 Gy to investigate the morphological features of radiation-induced cell death. Male p53 knockout mice, homozygously null p53(-/-) and heterozygous p53(+I-) mice (CBA/OYC), and wild type mice (CBA/OYC) were irradiated with a single dose of 5.0 Gy to determine whether the radiation- induced cell death was p53-dependent.The radiation-induced cell death of spermatogonia reached a peak at 12 hours after irradiation, but that of other tissue was at 6 hours after irradiation. Nuclei of many abnormal spermatogonia were condensed and TUNEL-positive, though margination of nuclear chromatin and nuclear fragmentation was rare. The incidence of radiation-induced cell death in testis was markedly increased in p53(+I+) mice, but there was little change in p53(-/-) mice. Apoptosis of lymphocytes and fibrosarcoma cells inceased markedly following irradiation in the p53(+/+) or p53(+/-) genotype, but that increased just a little in the p53(-/-) genotype.Spermatogonial cell death induced by irradiation is compatible with p53-dependent apoptosis, though the morphological features are not always typical.