M Valizadeh - Department of Biology, Faculty of Sciences, Urmia University
V Nejati - Department of Biology, Faculty of Sciences, Urmia University
A Shalizar-Jalali - Department of Basic Sciences, Faculty of Veterinary Medicine, Urmia University
E Hossien Najdgerami - Department of Biology, Faculty of Sciences, Urmia University

Background: Many studies have reported the damage heat stress can put on reproductive function and its role on human and animals infertility.Heat stress can elevate negative effects on testicular tissue de-pending on its severity. Temperature rise in mammals with ex-ternal testis can cause inflammation of tunica albuginea, thick-ening of the testicular capsule, as well as increased space in seminiferous tubes.Tunica albuginea is a connective tissue made up of fibrocytes and collagen filaments and as all other organs, testicular capsule serves as a supportive tissue for its parenchima.Tunica albugineas contracting function, being caused by myofi-brocytes and smooth muscle cells, has been proven.This contractive feature shows different physiological func-tions including elevation of sperm transition from testis to epididymis, maintenance of interstitial pressure inside the testis and controlling blood stream.Materials and Methods: For this experimental study Twenty-eight adult male rats (4 months of age, 180-220g body weight) were obtaind from the Experimental Animal Production Center of the Science Faculty of Urmia University. All the animals were housed in special cages and had free access to tap water and to a pelleted commercial laboratory animal chow. Animal room temperature and relative humidity controls were set at 22±2°C and 50±10%, respectively. lighting was controlled to give a 12-hour light and dark cycle.Animals were randomly categorized into 4 groups; group 1 served as a control, groups 2, 3 and 4 were heat-stressed (37, 39 and 43°C for 20 min per day, respectively). The HS was induced through immersion of experimental rat scrotums in a water bath. After 35 days, the testicles were harvested, then de-hydrated , cleand in xylene and embedded in paraffin wax. Thin sections were cut and stained with hematoxyline and eosin for histopathological analysis. inflammatory alterations of testicu-lar tunica albuginea were analyzed in all experimental groups. Results: In HS-exposed groups, testicular tunica albuginea in-flammation rate showed significant increase in a temperature-dependent manner compared to the control group.Conclusions: Any decrease in transitional sperm can be due contractive disorder in muscle cells of testicular capsule. These finding indicate that disorders in smooth cells of tunica albuginea may lead to infertility.