Effects of Chronic Hypoxia on Renal PDGF-A, PDGF-B, and VEGF Gene Expression in Rats

Abstract

Background: There is evidence from in vitro studies to suggest that the genes of platelet-derived growth factor (PDGF), and vascular endothelial growth factor (VEGF) are, like the erythropoietin gene, regulated by oxygen tension. Hypoxia-induced stimulation of, for example, PDGF or VEGF might be involved in the pathogenesis of acute or chronic renal failure and in renal ‘inflammatory’ diseases (glomerulonephritis, vasculitis, allograft rejection). Methods: Male Wistar rats were exposed to chronic normobaric hypoxia (10% O₂, 90% N₂) for 4 weeks. Additional groups of rats were treated with the endothelin receptor antagonist LU13525 and the NO donor molsidomine. Renal mRNA levels of PDGF-A, PDGF-B, and VEGF were semiquantitated using RNase protection assays. Results: Renal gene expression of PDGF-A and PDGF-B was neither affected by 2 or 4 weeks of hypoxia nor by concomitant treatment with LU135252 or molsidomine. Chronic hypoxia did also not change VEGF gene expression; however, concomitant treatment with LU135252 increased all VEGF subtypes (188, 164, 120). Conclusions: The findings of the present study suggest that renal PDGF and VEGF gene expression in vivo during chronic hypoxia for 2 and 4 weeks is not sensitive to tissue hypoxia in contrast to cell culture experiments. During chronic hypoxia with concomitant blockade of endothelin receptors, all VEGF subtypes were increased, suggesting an inhibitory action of endothelins with regard to renal VEGF gene expression.