Chronic hypoxia induced down-regulation of angiotensinogen expression in rat epididymis

The presence of an intrinsic renin-angiotensin system (RAS) in the rat epid idymis has been previously established by showing the expression of several key RAS components, and in particular angiotensinogen, the indispensable e lement for the intracellular generation of angiotensin II. In this study, t he possible involvement of this local epididymal RAS in the testicular effe cts of chronic hypoxia was investigated. Semi-quantitative reverse-transcri ption polymerase chain reaction (RT-PCR), Western blotting and by in situ h ybridization histochemistry of the rat epididymis were used to show changes in localization and expression of angiotensinogen. Results from RT-PCR ana lysis demonstrated that chronic hypoxia caused a marked decrease (60%) in t he expression of angiotensinogen mRNA, when compared with that in the normo xic epididymis. Western blot analysis demonstrated a less decrease (35%) in the expression of angiotensinogen protein. In situ hybridization histochem istry showed that the reduced angiotensinogen mRNA in chronic hypoxia was s pecifically localized to the epididymal epithelium from the cauda, corpus a nd caput regions of the epididymis; a distribution similar to that of normo xic rats. It was concluded that chronic hypoxia decreases the transcription al and translational expression of angiotensinogen, and thus local formatio n of angiotensin II, in the rat epididymis. (C) 2001 Elsevier Science B.V. All rights reserved.