Endothelin-1, endothelin-3 and their receptors (endothelin_A and endothelin_B) in chronic renal transplant rejection in rats¹

Abstract

Endothelins (ET) are a family of vasoactive peptides that play an important role in several disorders affecting kidneys. In this study we investigated the expressions of ET-1, ET-3, and their receptors, ET_A and ET_B, in a rat chronic renal transplant rejection model. Renal allografts were performed (F344 → Lewis) with bilateral nephrectomy in recipients. For isograft control, lewis → lewis transplantations were performed. All recipients were sacrificed 140 days after transplantation and the grafts were analyzed histologically. ET-1 and ET-3 protein expression in grafts was measured by immunohistochemistry and ELISA. Semiquantitative RT-PCR methods were used for mRNA levels of ET-1, ET-3, ET_A and ET_B. No evidence of chronical rejection was manifested in isografts. The allografted rats showed proteinuria and increased serum creatinine levels. Histologically, renal allografts showed atrophy and sclerosis of the glomeruli, cortical scarring and vascular intimal thickening. Immunohistochemically, ET-1 and ET-3 were localized in the convoluted tubules, collecting ducts, endothelium and smooth muscle cells of the large blood vessels. Significantly increased staining for ET-1 and ET-3 were found in allografts compared to isografts. Simultaneously, ELISA for ET-1 and ET-3 showed elevated protein concentrations in allografts compared to isografts. Allografts showed significantly increased ET-1- and ET-3 mRNA compared to isografts. On the other hand, a significant down regulation of the ET_A mRNA was noted, and the ET_B mRNA remained unchanged. The data from the present study suggest that alteration of ET system may be of importance in the pathogenesis of chronic renal transplant rejection.