Mechanoluminescence: lymphocyte analysis after exposure to ionizing radiation Valeriy E. Orel,* Igor N. Kadyuk, Natali N. Dzyatkovskaya, Michael I. Danko and Yuri I. Mel'nic Physics-Technical Laboratory, Ukrainian Research Institute of Oncology and Radiology, Lomonosova St. 33/43, 252022 Kyiv-22, Ukraine Received 18 May 1998; accepted 6 January 1999 ABSTRACT: Lymphocyte mechanoluminescence (ML) develops as a result of mechanochemical activation of cells. This paper describes devices (tribogenerators) and techniques for lymphocyte mechanoluminescence analysis. At different stages of the cellular cycle the ML of non-irradiated peripheral blood lymphocytes (PBL) showed characteristic differences. After 60 Co g -irradiation of PBL in vitro at 0.25 Gy and 1 Gy an alteration of ML was observed with a relationship between ML values of lymphocytes, and also of mitochondria (MT), and the dose of ionizing radiation used. By using bioluminescence techniques it was shown that g-irradiation reduces the amount of ATP synthesized by PBL in the stationary phase. Copyright # 2000 John Wiley & Sons, Ltd. KEYWORDS: mechanoluminescence; lymphocytes; mitochondria; ionizing radiation INTRODUCTION Lymphocyte mechanoluminescence (ML) or tribolumi- nescence develops as a consequence of mechanical activation and is due to the dissipation of mechanical into chemical energy. This is accompanied by a mechanoelectrochemical process of electric discharge generation and free-radical biosubstrate oxidation pro- cesses (1). This mechanism may be represented by the following equations:   " 0 " H ÁÈ  kT e ln n i  HE   1 d dt  X i W i n i 2 where: s = the surface density of the charge; " 0 = an electric constant; " = a relative dielectric penetrability; DΦ = work function; k = Boltzman constant; T = thermo- dynamic temperature; e = electron charge; n i = particle concentration; H = distance between electrization surfaces; E = electrostatic field strength. Equation 2 describes the process of microdischarge between di- electric barriers, where W i = drift velocity of electrons, ions, photons, neutral atoms and molecules. Mechanical activation of bio-objects does not lead to photon emission. Excited states occur as a result of radical-chain oxidative reactions, and the optical emis- sion is due to recombination of free radicals, as shown in equation 3: I  ! e  r 3 where ! = speed recombination reaction of free radicals;  e = excitement exit;  r = emission yield. It was found earlier that lymphocyte ML depends on the mechanochemical factors deforming the surface and shape of certain cellular organoids. The conformational changes in the superspiral structure of nuclear DNA and swelling and compression of lymphocyte mitochondria (MT) influence the ML. Values of lymphocyte ML show characteristic differences at various stages of the cellular cycle (2, 3). It is well known that the biological effect of ionizing radiation results in a significant growth in the number of lymphocytes with damaged membranes and distorted cellular shape. During the post-irradiation period, using electron and light microscopes, an atypical nuclear shape was observed with an increased incidence of chromoso- mal aberrations, while the cytoplasm contained predo- minantly only MT of small oval shape with transversely located cristae (4). The lymphocytes showed a reduced synthesis of ATP, which is the major bioenergetic source of mechanochemical events (5). Ionizing radiation exerts a significant influence on lymphocyte ML (6). Peripheral blood lymphocytes (PBL) possess high radiosensitivity depending on the stage of the cell cycle (7), and this paper presents a comparative investigation of the features of ML during various stages of the PBL cell cycle in rats after irradiation with relatively low doses of ionizing radiation. Luminescence 2000;15:29–36 *Correspondence to: V. E. Orel, Physics-Technical Laboratory, Ukrainian Research Institute of Oncology and Radiology, Lomono- sova St. 33/43, 252022 Kyiv-22, Ukraine. E-mail: orel@ucr.kiev.ua Copyright  2000 John Wiley & Sons, Ltd. CCC 1522–7235/2000/010029–08 $17.50 ORIGINAL RESEARCH