The Effect of Tritiated Water on the Development of the Rat Oocyte after Maternal Infusion during Pregnancy

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Abstract
The effect of continuous exposure in utero to tritiated water (HTO) was studied in the post-natal oocyte development of Wistar rats. Pregnant rats were given daily doses of 290 μCi to 5800 μCi HTO intravenously from the ninth day of pregnancy until term. During the first 21 days of life, a dose-dependent reduction of oocyte number was observed. A dose of 1450 μCi decreased the total oocyte number to 50 per cent of the controls. Accelerated maturation of oocytes was not demonstrable. The highest dose of 5800 μCi produced total aplasia in the ovaries. The number of oocytes is apparently one of the most sensitive parameters of β-irradiation damage. A comparison with data after continuous 3H-thymidine (3H-TdR) application showed a ten times higher effect of 3H-TdR compared with HTO. The mechanisms for this phenomenon are discussed, and it is concluded that the final position of the tritium compound in the cells is the most important factor in the radiobiological effect.