The effects of the time interval in fractionated x-ray treatment of mouse spermatogonia

The relation between induced reciprocal translocations and cell killing of mouse spermatogonial stem cells after combined treatments with hydroxyurea and X-rays

The induction of reciprocal translocations in mouse spermatogonial stem cells, visualised in dividing primary spermatocytes, was studied after combined treatments with hydroxyurea (250 and 500 mg/kg) and X-rays (6, 8 and 9 Gy). The time intervals between the 2 treatments were 16 h (leading to extremely high cell killing) and 48 h (giving rise to less killing than irradiation alone). Comparison of the observed frequencies of translocations with reported data on stem cell killing (de Ruiter-Bootsma and Davids, 1981) show that the ratio between the probabilities that a radiation-induced basic lesion kills a cell or produces a translocation, theoretically calculated by Leenhouts and Chadwick (1981) to be about 10, can indeed be confirmed experimentally.

Protective effect of hypoxia in the ram testis during single and split-dose X-irradiation

Spermatogonial stem-cell survival in the ram was studied after single (6 Gy) and split-dose (2 x 3 Gy, interval 21-24 h) X-irradiation both under normal and hypoxic conditions. Hypoxia was induced by inflation of an occluder implanted around the testicular artery. The occluders were inflated about 10 min before irradiation and deflated immediately after. Stem-cell survival was measured at 5 or 7 weeks after irradiation by determination of the Repopulation Index (RI) in histological testis sections. The RI-values after fractionated irradiation were only half those after single dose irradiation. Hypoxia had a protective effect on the stem-cell survival. After split-dose irradiation under hypoxic conditions two times more stem cells survived than under normal oxic conditions; the RI-values increased from 34% (oxic) to 68% (hypoxic). This effect of hypoxia was also found after single dose irradiation where the RI-values increased from 68% (oxic) to 84% (hypoxic). The development of the epithelium in repopulated tubules was also studied. Under hypoxia, a significantly higher fraction of tubules with complete epithelium was found after single (38 vs. 4%) as well as after split-dose irradiation (12 vs. 0%).

Survival of spermatogonial stem cells in the rat after split dose irradiation during LH-RH analogue treatment

A rat model has been created in which a single injection of an LH-RH analogue depot preparation (Zoladex, ICI 118630) produced a temporary interruption of the pituitary-gonadal axis. This effect applied during irradiation was investigated as a possible mechanism to protect the testis from radiation damage. A local testicular irradiation dose of 6.0 Gy was given either as a single dose or as a fractionated (2 X 3.0 Gy) dose at different time intervals ranging from 8 to 72 h. Stem cell survival was measured 11 weeks after irradiation by means of the repopulation index and the number of haploid cells (spermatids) measured by flow cytometry. Serum gonadotrophins and testosterone concentrations were measured to evaluate hormonal recovery. No significant differences were observed between serum concentrations of follicle-stimulating hormone (FSH), luteinizing hormone (LH) and testosterone and the duration of the fractionation interval. Stem cell survival was higher following fractionated irradiation in comparison with the single dose. For the 8 h interval an increase in recovery ratio was found, amounting to a factor of 5 of the single dose value. The fluctuating pattern of the recovery curves indicated changes in radiosensitivity of stem cells. The combination of hormonal inhibition of spermatogenesis and fractionated irradiation led to a decrease in the absolute numbers of stem cells. However, the stem cell recovery curves were identical to those seen without hormonal inhibition. It was concluded that hormonal pretreatment with Zoladex during split dose irradiation had no protective effect on stem cell survival.

The influence of radiation on fertility in man

Increasing numbers of young people are now being cured of certain neoplasms by radiotherapy and chemotherapy. Such people will naturally wish to lead a normal life and possibly to have children. Therefore the question of the effect of radiation and cytotoxic drugs on the reproductive capacity of these patients has become important. The purpose of this report is to review the information available on the effect of radiation on fertility in man. Direct information on radiation effects on human fertility is available from reports on therapeutic exposure and deliberate experimental exposure. Although the total number of cases involved is small, a number of general principles emerge. In males, fractionated irradiation of the testes may be more harmful than acute, at least up to total doses of about 600 cGy (rad). Fractionated doses greater than 35 cGy cause aspermia, the time taken for recovery increasing with dose, and after more than 200 cGy aspermia may be permanent. In females, response varies with age as well as dose. For example, 400 cGy may cause a 30% incidence of sterility in young women, but in women aged above 40 years it results in 100% sterility. However, individuals of either sex show a degree of variation in their response to irradiation.