100STRUCTURAL ALTERATIONS IN SPLEEN AND KIDNEY IN RESPONSE TO GRADED HEAT STRESSThe term ‘heat related illnesses’ refers to a plethora of medical conditions resulting from prolonged exposure to hot environment. These include relatively mild heat cramps to life threatening heat stroke wherein the core body temperature rises beyond 40°C. Heat stroke is marked by central nervous system dysfunction: delirium, convulsions, or coma. Objective: There is a need to investigate the pathophysiology of heat stroke, as till date, the diagnosis and treatment of heat stroke is unsatisfactory. The literature on heat stroke is predominated by central nervous system investigations and findings. This study has been undertaken with the objective of examining the pathophysiology of organ damage in Rat. Methods: The effect of graded heat stress culminating in heat stroke has been investigated in Rat Kidney and Spleen by subjecting Rats to heat exposure at 45ºC and 30% RH for varied time durations till the attainment of desired value of core body temperature. Results: In kidney, loss of tubular integrity and luminal casts has been found to increase in severity with the degree of heat stress. On the other hand, spleen has been observed as relatively resistant to heat stress, exhibiting structural alterations only under the condition of heat stroke induced death. Conclusion: This study revealed a direct correlation between the intensity of organ damage and the magnitude of heat stress. This study combined with biochemical and genetic level studies is likely to give deep insights into the pathophysiology of heat related illnesses.directordipas@gmail.comResearch532015Heat stroke,Histology,Kidney,Hyperaemia,Spleen,Red pulp,White pulpMedha Kapoor,Nishant Ranjan Chauhan,B.N. Mishra,R.K. Khandal,Sarita Nanda,Shashi Bala SinghDefence Institute of Physiology and Allied Sciences, Defence Research and Development Organisation, Timarpur, Lucknow Road, New Delhi 110054, India,Biochemistry Department, Daulat ram College, University of Delhi, North Campus, New Delhi, India,IET campus, Uttar Pradesh Technical University, Sitapur road, Lucknow, India.,IET campus, Uttar Pradesh Technical University, Sitapur road, Lucknow, India.,Biochemistry Department, Daulat ram College, University of Delhi, North Campus, New Delhi, India,Defence Institute of Physiology and Allied Sciences, Defence Research and Development Organisation, Timarpur, Lucknow Road, New Delhi 110054, India