Magnetic Field Affects Thymidine Kinasein Vivo

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Abstract
Whole mice on normal or vitamin E deficient diet were immobilized by Nembutal anaesthesia and exposed to a stationary magnetic field of 1·4 tesla for up to 60 min. Thymidine kinase (TdR-K) was assayed in the high-speed supernatant of bone marrow cells which were collected into optimally adjusted nutrient medium of pH 7·3–7·4 containing 1350 mg NaHCO3 per litre and were then destroyed by sonication. In parallel, uptake of 125I-labelled 5-I-2′-deoxyuridine (125IUdR) into DNA of whole bone marrow cells, of various tissues and of the whole body was measured. The results indicate the following. The magnetic field exposure caused in bone marrow cells an increase of activity of TdR-K and of uptake of 125IUdR to about 130 per cent of control. The effect depended on immobilization of the mice in the field and on the presence of NaHCO3 in the nutrient medium used for cell collection. There was no field-induced change in body temperature. The effect on 125IUdR uptake was similar in isolated tissues and the whole body following intraperitoneal injection of the tracer. It increased to a maximum of about 135 per cent of control, during exposure times over 30 min. This effect is not explained as a result of a temporary change in the rate of cell proliferation. Vitamin E deficiency caused a depression of activity of TdR-K and of uptake of 125IUdR in bone marrow cells to about 75 per cent of control. This depression was similar to that observed after whole body γ-irradiation with about 0·01 Gy (1 rad). The inhibitory effects of vitamin E deficiency on TdR-K were overcome by exposure to the magnetic field. Immediately after cessation of the magnetic field for 60 min, 125IUdR uptake was normal; normalization of uptake was delayed with exposure times shorter than 60 min. A 60 min exposure to the magnetic field had no long term effect on turnover of labelled cells in the mice. The data imply the non-specific control of thymidine kinase by charged molecular species and the modification of this control by the magnetic field.