Effect of UVB radiation on human erythrocytes in vitro

In order to evaluate the UVB radiation induced phototoxic effect, the human erythrocytes (RBCs) were used an alternate biological model and rate of photohaemolysis was assessed in vitro at various intensities of UVB radiation (0-2.0 mW/cm2) for an exposure period of 0-240 min. The alterations of biochemical activities in RBC membrane (ghosts), caused by its exposure under an average incident intensity of UVB radiation (0.5 mW/cm2) in sunlight at earth surface, were also determined to understand the possible mechanism of photohaemolysis. We observed UVB dose dependent lysis of erythrocytes by recording haemoglobin and methemoglobin (oxidized form of haemoglobin) in photohaemolysate. We also observed significant inhibition in ATPase, acetylcholinesterase, glucose-6-phosphate dehydrogenase activites and an increased amount of thiobarbituric acid-reactive substance (TBA-RS) in RBC ghosts exposed to UVB radiation (0.5 mW/cm2) for a period of 0-100 min (doses: 0, 0.33, 0.66, 1.0, 1.5 and 3.0 J). The changes were found UVB dose dependent. A decrease of glutathione content in RBC ghosts at low dose level of UVB exposure (0.33 J) was found to be recovered at higher dose levels (0.66-1.5 J). These observations suggested, UVB dose dependent toxicity to human erythrocytes in vitro. Thus the erythrocytes can be used for an assessment of UVB induced biological effects and to understand possible mechanism of the phototoxicity.