PARENT SESSION
PLATFORM SESSION 2. MOLECULAR SIGNALING EVENTS IN THE MALE REPRODUCTIVE TRACT

Sunday, August 1, 2004
3:00 PM–5:00 PM
Buchanan A204
Chair: Jaques Tremblay Co-Chair: Maureen McAuliff

(13) HYPOXIA INDUCIBLE FACTOR-1 EXPRESSION IN THE MURINE TESTIS.

Turner, Terry¹, Zeng, Shuqiu¹, Palmer, Lisa², Lysiak, Jeffrey¹, ¹ University of Virginia, Charlottesville, VA² University of Virginia, Charlottesville, VA

ABSTRACT- Hypoxia inducible factor (HIF)-1 is a transcription factor that plays an essential role in oxygen homeostasis. HIF-1 is constituatively made in cells; however, it is ubiquitinated and degraded under normoxic conditions. Hypoxia prevents the ubiquitination of HIF-1, results in stabilization of the protein, and leads to target gene activation. Some proteins regulated by HIF-1 are known to be expressed in the testis where spermatogenesis occurs within seminiferous tubules never penetrated by the vasculature. Because of its vascular arrangement and the high metabolic demand of spermatogenesis the testis has previously been described as functioning on the brink of hypoxia; thus, we have hypothesized that HIF-1 is constituatively expressed and stabilized in the testis offering the potential that the protein plays a role in testicular homeostasis. To this end we performed western blot analysis and immunohistochemistry to determine if HIF-1 is expressed in the murine testis. Western blot analysis of nuclear proteins from liver, kidney, and testis revealed HIF-1 present only in the testis. HIF-1 was detected as 2 prominent bands at approximately 115 - 120 kDa. Immunohistochemical localization revealed specific labeling of HIF-1 in Leydig cells only. Subjecting the testis to periods of acute ischemia (0.5 hr-4 hr) did not result in an increase in HIF-1, but preliminary data indicate that testicular HIF-1 does increase after two weeks exposure of male mice to hypoxic conditions (10% atmospheric oxygen). Thus, HIF-1 is constituatively present in the murine testis and it is not upregulated after periods of acute ischemia. This is in contrast to the absence of HIF-1 in other normoxic tissues and suggests a role for the transcription factor in testicular homeostasis, particularly in the Leydig cells where the protein was localized. Preliminary evidence suggests the testis does have the capacity to increase HIF-1 after chronic hypoxia. Studies are currently underway to determine if HIF-1 is phosphorylated in the testis and to identify potential downstream targets. Supported by NIH DK53072.

KEY WORDS: testis, hypoxia inducible factor, Leydig cells