Copyright © 2014 Ayobola Abolape Iyand, Dapo Pius Oparinde. This is an open access article distributed under the Creative Commons Attribu- tion License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. International Journal of Biological Research, 2 (2) (2014) 81-83 International Journal of Biological Research Journal home page: www.sciencepubco.com/index.php/IJBR doi: 10.14419/ijbr.v2i2.3163 Research Paper An investigation of the cause of death in Wistar rats exposed to sunlight: focus on tissue histology Ayobola Abolape Iyanda, Dapo Pius Oparinde* Department of Chemical Pathology, College of Health Sciences, Ladoke Akintola University of Technology, Osogbo, Nigeria *Corresponding author E-mail: dpoparinde@lautech.edu.ng Abstract Objective: The aim of the study is to investigate the effects of ultraviolet rays of the sun on organs like the liver, brain, heart, kidney, lung and ileum. Methods: Fourteen female rats (235 g) were used for the study and equally distributed into 2 groups. While the rats in the test groups were left in an open place for a period of 7 hours daily for adequate exposure to sunlight, control rats were kept in cages at ambient tem- perature of 26°C in the animal house. When all the animals died on the 10th day of study, samples of different tissues were obtained, fixed in 10% neutral buffered formalin and stained with hematoxylin and eosin (H & E). Results: 100% mortality was recorded. Results showed no visible lesion for all the tissues of control rats whereas pathological features like severe congestion of the coronary vessel and mild pulmonary congestion as well as thickening of alveolar wall were reported for heart and lung respectively in sun-exposed rats. Moreover, in sun-exposed rats other tissues such as the brain, ileum, kidney and liver showed no visible lesion. Conclusion: From the outcome of this study, it may be inferred that excessive sun exposure can be a cause of mortality in a nocturnal animal species, with death resulting from multi-organ damage. Keywords: Daily Exposure, Mortality, Rat, Sunlight, Tissues. 1. Introduction The Sun emits ultraviolet B (UVB) radiation (290-315 nm) that affects human health in both harmful ways such as skin cancers and beneficial ones like vitamin D3 production. The extent to which sun exposure can be linked to health has been revealed by Godar et al. (2011). These workers reported that there is an asso- ciation between deficient or insufficient serum 25-hydroxyvitamin D concentrations of young Americans (≤19 yr.) who seem inade- quately exposed to sun because of sunscreen. Although there are other findings that seem to be in conflict with that, those studies indicated that people are capable of making sufficient vitamin D3 from their “casual,” or every day, outdoor exposures even if they diligently use sunscreens with sun protection factor. Barsh (2003) reported a wider role for the sun in relation to human existence. According to the results of that study while it is well known that UVB has medical effects such as synthesis of vitamin D, it also has been linked with sunburn. In addition, as a result of its antiseptic properties it is sometimes used to sanitize tools and water. According to the author, since ultraviolet light is strongly attenuated by Earth's ozone layer, this means that the amount of UV varies greatly with latitude and has been partially responsible for many biological adaptations, including variations in human skin color in different regions of the world (Barsh, 2003). Worldwide the incidence of skin cancer is on the increase. Some of the primary preventive activities that have been put forward by cancer agencies include protecting the skin from the sun by wear- ing protective clothing, using a sunscreen with appropriate sun protection factor, wearing a hat, and avoiding the sun (Stanton et al. 2004). Skin disorders are the most prominent pathological con- ditions associated with excessive sun exposure and abnormal skin histology has been observed in experimental animals exposed to UVB. Because these disorders are oxidative-stress mediated, ab- normal histological manifestations of other tissues cannot be dis- counted. Therefore, the aim of this study is to examine histologic presentation of the brain, heart, lung and ileum of rats that died as a result of exposure to the sun and possibly identify the cause of death. 2. Materials and methods 2.1. Care of experimental animals A total of 14 female Wistar rats of average weight of 235 g were used for the study. The animal experiment was carried out at the Experimental Animal Unit of Faculty of Veterinary Medicine, University of Ibadan, Nigeria. While the rats in the test groups were left in an open place for a period of 7 hours daily, control rats were kept in cages at average ambient temperature of 26°C. The study took place from 8 th to 17 th February 2012; with the weekend of 11 th and 12 th being excluded. Seven of the rats consti- tuted the sun-exposed group and the other seven rats served as control. Each day, exposure was for a period of 7 hours starting from 9:00 to 16:00. No form of sun-screening was employed to protect the sun-exposed group; rather they were left in an open field. The control rats were kept in cages in the animal house. All experimental animals were supplied feed and water without any form of restriction. The procedures were carried out in accordance with national and international laws and Guidelines for Care and