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Effects of Heat and Cold on Edema Formation Produced by Topical Prostaglandin E1 in vivo

Jenny Bryant and Christopher M. Quick

College of Veterinary Medicine, Department of Physiology,

Michael E. DeBakey Institute Department of Biomedical Engineering

Prostaglandin E1 (PGE1), synthesized from arachidonic acid, is released from endothelial cells in an inflammatory response to increase both leukocyte movement to the inflammation site and the rate of waste removal from the area. By manipulating the vascular tone and the permeability of the blood vessel walls, PGE1 acts as a potent vasodilator and plays a role in the formation of edema in the inflamed area. Applications of heat and cold are used to reduce edema resulting from inflammation. Although heat and cold can have therapeutic antiphlogistic effects, different inflammatory edemas are inhibited or enhanced by the application of cold and heat. Edema formed from the vasodilating actions of PGE1 is relieved by heat and aggravated by cold. This is counterintuitive because a hypothermic condition should induce vasoconstriction of the blood vessels and reduce edema, not aggravate it. This study is expected to show that the vasodilating effects of PGE1 override the vasoconstrictive mechanisms of temperature control. In the study, the Pallid bat wing will be used as a model because it allows for the observation of the microvasculature without the effects of anesthesia or trauma. The two-dimensional non-pigmented wing can be transilluminated and viewed non-invasively with an intravital microscope. Blood vessel diameter, blood flow, wing temperature, frequency of lymphatic pumping and edema formation will be measured before and after the topical administration of PGE1 at temperatures of 21C, 26C, and 31C. Edema formation will be calculated by measuring wing thickness. After the application of PGE1 at 21C, blood vessel diameter, blood flow, and edema formation will increase, and wing temperature and frequency of lymphatic contractions will decrease.   It is predicted that after the topical application of PGE1 at 26C, the wing temperature will decrease, vessel diameter, blood flow, and edema formation will increase and frequency of lymphatic contractions will remain the same. It is also predicted that wing temperature, vessel diameter, and blood flow will remain the same at 31C after the application of PGE1, but lymphatic pumping will increase, and as a result edema formation will decrease. However, results of this study are being collected