*Corresponding Author: Dr.Subodh Kumar Yadav, Email: dr_subodh@hotmail.com, Phone No: +977-9842287013 ISSN 0976 – 3333 ORIGINAL RESEARCH ARTICLE Available Online at www.ijpba.info International Journal of Pharmaceutical & Biological Archives 2012; 3(3):539-544 Experimental Study of Effects of Heat Stress on Rat’s Liver Subodh Kumar Yadav *1 , Renu Yadav 2 , Bijay Aryal 3 and Soumya Bhattacharya 4 1 Department of Human Anatomy, 2 Department of Physiology and 3 Department of Clinical Pharmacology,Chitwan School of Medical Sciences P.Ltd, Bharatpur-10, Chitwan , Nepal 4 Department of Human Anatomy, B.P. Koirala Institute of Health Sciences, Dharan, Nepal Received 06 Mar 2012; Revised 02 Jun 2012; Accepted 09 Jun 2012 ABSTRACT In animals and humans, some physiological and biochemical adaptations could occur to protect essential cell functions against the heat stress and to permit a rapid recovery from moderate hyperthermic damage. However, each tissue and organ has a different sensitivity for sustaining thermal injury. Hence, the present study was undertaken to study histological and pathological changes due to chronic heat stress on rat’s liver. Thirty albino wistar rats weighing about 150-200gms in experimental group were kept in increased room temperature (i.e 38±2°C) for 15 days. Halogen heater maintained room temperature. Similarly, thirty albino wistar rats weighing about 150-200gms in control group were kept in normal room temperature (i.e 26±5°C) for 15 days. Room temperature was maintained by air conditioner. After 15 days, rats were sacrificed by cervical dislocation, liver tissues were removed and histological slides were prepared. This study showed various changes occur in length and breadth of rat’s hepatocyte cell whereas it didn’t have any effect on weight of rats. This study provides evidences in support of necrosis, inflammatory changes, irregular cell membrane, enlarged nucleus, binucleated cell, dilated hepatic venules and dilated sinusoids of experimental group of rat’s liver in compare to control group. Key words: Hyperthermic damage, albino wistar rats, dilated hepatic venules and sinusoids. INTRODUCTION Exposure to excessive heat adversely affects on health and known as heat stress. This Colloquialism is a source of confusion because in the scientific literature "heat stress" is synonymous with "heat load," which carries the connotation that adverse health effects will occur only if the heat stress exceeds the person's heat tolerance capacity [1] . At lower levels of heat stress there is no risk of health damage, to be even though a person may feel discomfort. ldeally, it would be desirable eliminate heat stress completely by keeping the work place at a comfortable temperature because the state of discomfort has many adverse behavioral effects, such as reduced work rate, increased irritability, carelessness, and a feeling of fatigue [2] Typical hyperthermia sometimes occurs during severe heat waves in summer and because of hard exercise throughout the world . These effects may render a worker more prone to accidental injuries. Unfortunately, the cost of keeping all job sites at comfortable temperature is not possible. [3,4] . In some temperate large cities, extreme heat stress is associated with an enhanced heat island effect. The incidence of heat-related morbidity, such as heat stroke in aged persons, has been increased because of exposure to extremely hot temperatures in summer. Heat stroke is caused by severe hyperthermia, and rectal temperatures of typical patients are higher than 40°C. Many organs such as liver, kidney and central nervous system (CNS) are damaged by severe hyperthermia [5, 6] . Thrombus, infarct, and death from heat stroke may be caused by injury of these organs. In animals and humans, some physiological and biochemical adaptations could occur to protect essential cell functions against the heat stress and to permit a rapid recovery from moderate hyperthermic damage [7,8,9,10] MATERIALS AND METHODS . However, each tissue and organ has a different sensitivity for sustaining thermal injury. Hence the present study was undertaken to study histological and pathological changes due to chronic heat stress on rat’s liver. Animal handling