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1 April 2004 Expression and Localization of Hypoxia-Inducible Factor-1 Subunits in the Adult Rat Epididymis
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The epididymal epithelium contributes to formation of a luminal fluid that is essential for the protection of spermatozoa from a variety of insults including changes in oxygen tension. A key regulator of the response to oxygen debt in many cells is hypoxia-inducible factor-1 (HIF-1). A transcription factor composed of α and β subunits, HIF-1 activates genes that mediate oxygen homeostasis and cell survival pathways or trigger cell death responses. Previously we have shown that HIF-1α mRNA is expressed in the adult rat epididymis. Goals of this study were to determine whether HIF-1α protein is activated by ischemia in the rat epididymis, to determine whether epididymal HIF-1α mRNA expression is androgen dependent, and to identify epididymal cell types expressing HIF-1α and β. Immunoblot analysis revealed that HIF-1α protein is primarily present in corpus and cauda of the normoxic epididymis and unaffected by ischemia, whereas HIF-1β was detected equally in all regions and also unaffected by ischemia. HIF-1α mRNA expression in all regions was not affected by 15 days bilateral orchiectomy. Principal cells stained positive for HIF-1α by immunocytochemistry, with the epithelium of initial segment and caput epididymidis staining less intensely than corpus and cauda. HIF-1β immunoreactivity was equally present in principal cells in all regions. Clear, narrow, and basal cells were unreactive for HIF-1α and β. The presence of HIF-1 in normoxic epididymis and the regional distribution of HIF-1α suggests fundamental differences in how proximal and distal regions of the epididymis maintain oxygen homeostasis to protect the epithelium and spermatozoa from hypoxia.

M. A. Palladino, J. D. Powell, N. Korah, and L. Hermo "Expression and Localization of Hypoxia-Inducible Factor-1 Subunits in the Adult Rat Epididymis," Biology of Reproduction 70(4), 1121-1130, (1 April 2004).
Received: 11 September 2003; Accepted: 1 December 2003; Published: 1 April 2004

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