Granulocytes' enzymes as biomarkers of radiotoxicity in individuals occupationally exposed to low-level radiation.

Purpose: To investigate the possibility of using the granulocytes' enzymes alkaline phosphatase (L-ALP) and myeloperoxidase (MPO) as biomarkers to study and analyse contamination of nuclear medicine personnel working with radionuclides (RN) when radiotoxic effects are very low, before occupational radiation illness or benign haematological disorders and malignant diseases have occurred. Also, to investigate the relationship between chromosomal aberrations in lymphocytes and the activity of L-ALP and MPO in neutrophil granulocytes (NphG).

Materials And Methods: The absorbed external doses of ionizing radiation (IR) were measured by thermoluminescent personal dosimeters (TLD) for the duration of occupational exposure (DOE). Urine radioactivity was measured by gamma- spectrometry. Venous blood was used for leukocyte count and search for chromosomal aberrations by conventional cytogenetic techniques. Blood smears were stained for L-ALP and MPO using a modified Kaplow's method and the classical method with benzidine dihydrochloride, respectively. The occupationally exposed group (E) consisted of 74 workers exposed to short-life radioactive isotopes I131 (beta and mostly gamma emission) and mTc99 (gamma emission). The control group (C) consisted of 52 subjects living in the same region, working in the same institution, occupationally not exposed to RN. A patients' group (P; n=31) took I131 or mTc99 for diagnostic purposes.

Results: Although the measured values did not exceed the yearly quota for professionally exposed individuals, characteristic chromosomal aberrations in peripheral blood lymphocytes (dicentrics, fragments, rings) were identified. L-ALP and MPO activity was inhibited in the NphG in occupationally exposed workers, especially in persons with chromosomal aberrations, working for a long time in ionizing radiations zones (p <0.01).

Conclusion: Decreased activity of L-ALP and MPO can reveal effects of long-lasting exposure to low-dose IR. A significant relationship between chromosomal aberrations in lymphocytes and activity of the enzymes in granulocytes was found.