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82Justyna Szymańska et al.ously frozen. Other experiments were carried out basingon freshly separated cells.Table VII. Results of experiment 6Tabela VII. Wyniki eksperymentu 6Parameters 10 mW 20mWControlEds [J/cm 2 ]2 4 82 4 8t [s]Test 1Test 2Test 3Test 4Test 5Test 6Medium70s 140s 280s 35s 70s 140sControl0.967 0.985 0.947 0.992 1.081 1.076 0.887 1.1110.943 0.976 0.939 0.990 1.014 0.995 0.950 1.0830.993 0.937 0.953 1.004 1.042 0.982 1.114 1.1470.845 1.095 0.938 0.907 1.028 1.156 1.043 1.0110.892 0.835 0.823 0.802 0.997 0.933 1.000 0.9250.619 0.75 0.725 0.776 0.887 0.863 0.852 0.8790.877 0.930 0.888 0.912 1.008 1.001 0.974 1.026Control % 96.13 101.96 97.33 98.26 97.55 94.96p NS NS NS NS NS NSIn the next, seventh experiment, the wavelengthwithin the range of infrared and deeper penetration –820 nm was applied. Six trials were carried out withpower of 100 mW and energy doses within the rangeof 2-8 J/cm 2 . Triple exposure to radiation was performedwith one-day intervals. The results are shownin Table VIII. The increase of proliferation (128% and117%) was noticed, as a result of the energy doses of 4J/cm 2 and 8 J/cm 2 application. However such an increase,as it was revealed in the first experiment wasnot achieved. In this trial the number of cells was decreasedto 5 000 per hole.Table VIII. Results of experiment 7Tabela VIII. Wyniki eksperymentu 7Parametry100 mWEds [J/cm 2 ] 2 4 8 Controlt [s] 7s 14s 28sTest 1Test 2Test 3Test 4Test 5Test 6MediumControl %p1.32 2.092 1.739 2.0351.837 1.774 1.751 1.7881.565 1.866 1.639 1.2041.175 2.042 1.705 1.2980.574 1.386 1.643 0.9480.422 0.638 0.472 0.3911.149 1.633 1.492 1.27789.94 127.84 116.77NS NS NSThere were six trials of irradiation characterized bythe wavelength of 808 nm and application of highintensitylaser of a power of 1500 mW as well as energydoses within the range of 2-8 J/cm 2 introduced inanother experiment. Double exposure to radiation wasperformed with a one-day interval. The results areshown in table IX. The high-intensity laser applicationcharacterized by the power of 1500 mW caused theincrease of endothelial cell proliferation whichamounted in turn to about 108% (for energy dose of 2J/cm 2 ) and 117% (for energy dose of 4 J/cm 2 ). Theincrease of proliferation was not noticed at the energydose of 8 J/cm 2 . The dose might have been too large,which inhibited multiplication of vascular endothelialcells.Table IX. Results of experiment 8Tabela IX. Wyniki eksperymentu 8Parameters1500 mWEds [J/cm 2 ] 2 4 8 Controlt [s] 2.3s 4.6s 9.3sTest 1Test 2Test 3Test 4Test 5Test 6Medium2.027 2.031 1.537 1.9382.126 2.12 2.003 1.8692.071 2.189 1.81 1.8772.01 2.279 1.793 1.8481.78 2.039 1.769 1.7951.697 2.015 1.466 1.5271.952 2.112 1.730 1.809Control %107.90 116.76 95.61p NS 0.0047 NSDISCUSSIONThe photobioactivation phenomenon, i.e. energyabsorption by photoreceptors needs to occur to enablethe laser irradiation to modulate the cellular processes.It is possible to observe the laser irradiation absorption(in microscale) by the components of respiratory chain(inter alia: cytochrome oxidase, NAD), which causesnumerous photochemical and photobiological changes.It is followed by the change of oxidation-reductionstate within mitochondria as well as cytoplasm. Theirradiation within the visible range (red) and near infraredwhich influences these structures contributes to thesynthesis modulation of DNA and RNA, which thencauses the cell proliferation [3]. Many researchersmade an effort to evaluate the influence of LLLT on invitro cell cultures. The research works concern usuallythe fibroblast [12-18] and osteoblast cultures [19-21].Not many works are devoted to the effect of laser irradiationon the vascular endothelial cells [22.23].Schindl’a et al. [22] evaluated the effect of endothelial