Summary:This study was aimed at demonstrating the immunohistochemical expression of VEGF and its receptors flt-1 and flk-1 in the testes and epididymis of the rabbit and at investigating the potential role of these molecules in testicular and epididymal physiology. The testes and epididymis of 15 male adult New Zealand rabbits constituted the material of the study. The streptavidinbiotin complex (ABC) immunohistochemical technique was used to determine the localization of VEGF and its receptors flt-1 and flk-1 in the testes and epididymis. In the testes, immunoreactivity for VEGF and its receptors flt-1 and flk-1 was observed in the Sertoli cells and spermatogonia in the seminiferous tubules throughout all of the spermatogenic stages from I to VIII and in the Leydig cells of the interstitium. Furthermore, immunoreactivity was also observed in the acrosome of the spermatids in seminiferous tubules for VEGF at stages V, VI, VII and VIII and in the acrosome of the spermatids at stages VII and VIII and the blood vessels of the interstitium for flk-1. Positive immunoreactivity, ranging from strong to weak, was detected for VEGF, flt-1 and flk-1 in the cytoplasm of the principal, apical, basal and clear cells of the epithelium lining the epididymal initial segment and the caput, corpus and cauda epididymidis. The specific localization of the VEGF protein and its receptors flt-1 and flk-1 in the testes of the rabbit suggests that these molecules could have a functional role in several processes, including spermatogonial differentiation, spermiogenesis, acrosome development in spermatids, steroidogenesis in Leydig cells, epididymal sperm maturation, and the maintenance of the bloodepididymis barrier.Keywords: Epididymis, rabbit, testis, VEGF, VEGF receptors. Tavşan testis ve epididimislerinde vasküler endoteliyal büyüme faktörü ve reseptörlerinin immunohistokimyasal lokalizasyonuÖzet: Bu çalışmanın amacı, VEGF ve reseptörleri flt-1 ile flk-1'in tavşan testis ve epididimisindeki immunohistokimyasal ekspresyonlarını belirlemek ve bu moleküllerin testis ve epididimis fizyolojisindeki potansiyel rollerini araştırmaktır. Çalışmada materyal olarak, 15 adet sağlıklı, erkek Yeni Zellanda tavşanından elde edilen testis ve epididimisler kullanıldı. VEGF ve reseptörleri flt-1 ile flk-1'in testis ve epididimisdeki lokalizasyonlarının belirlenmesi amacıyla streptavidin biotin kompleks (ABC) immunohistokimyasal yöntemi kullanıldı. Testiste, I'den VIII'e kadarki tüm spermatojenik evrelerde seminifer tubüllerdeki Sertoli hücreleri ve spermatogonialarda ve intersitisyumda Leydig hücrelerinde VEGF ve reseptörleri flt-1 ile flk-1 için immunreaktivite gözlendi. Buna ilaveten, seminifer tubüllerde V., VI., VII. ve VIII. evrelerde VEGF için, VII. ve VIII. spermatojenik evrelerde ise flk-1 için spermatidlerin akrozomlarında ve intersitisyumda kan damarlarında immunreaktivite belirlendi. Epididimiste, başlangıç segmenti, kaput, korpus ve kauda epididimidis epitelindeki prensipal, apikal ve bazal hücreleri ile clear hücrelerinin sitoplazmaların...