Selective downregulation of ETA receptor mRNA in renal transplant recipients on cyclosporin A revealed by quantitative RT-PCR.
Despite intensive investigation, a pathophysiological role for the endogenous vasoconstrictor peptide endothelin (ET) remains elusive. The kidney is particularly sensitive to the effects of ET, which are mimicked by the administration of cyclosporin A (CsA), and animal models suggest a role for ET in the vasoconstrictive effects of CsA. Using a recently validated novel fluorescent quantitative RT-PCR assay to enable the direct study of human renal biopsies, we have quantified mRNA for the two known ET receptor subtypes ETA and ETB in cortical tissue from three groups of patients: renal transplant recipients on CsA (n = 7), those with native renal disease (n = 5) and normal controls (n = 7). Median and mRNA levels (amol/microgram total RNA) were 0.024, 0.17 and 0.2 respectively for ETA and 0.57, 0.64 and 0.96 for ETB. These values indicate significant downregulation of ETA (P = 0.003) but not ETB (P = 0.104) mRNA in the transplant group. These results provide the first demonstration of a perturbation in the human ET system at tissue level in a pathophysiological situation, and suggest that the deleterious renal vasoconstrictor effects of CsA might be ameliorated by selective ETA receptor antagonism in the future. This study also illustrates the feasibility of ex vivo analysis of human diagnostic material at the molecular level.
Karet
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Clinical Pharmacology Unit, University of Cambridge, Addenbrooke's Hospital, UK.
Davenport
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D000328:Adult; D000368:Aged; D001483:Base Sequence; D016572:Cyclosporine / Q000009:adverse effects; D017931:DNA Primers / Q000235:genetics; D015536:Down-Regulation; D005260:Female; D006801:Humans; D007166:Immunosuppressive Agents / Q000009:adverse effects; D016030:Kidney Transplantation / Q000009:adverse effects / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000235:genetics* / Q000378:metabolism*; D044022:Receptor, Endothelin A; D044023:Receptor, Endothelin B; D017466:Receptors, Endothelin / Q000235:genetics*; D012079:Renal Circulation / Q000187:drug effects / Q000502:physiology; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology
D017931:DNA Primers; D007166:Immunosuppressive Agents; D012333:RNA, Messenger; D044022:Receptor, Endothelin A; D044023:Receptor, Endothelin B; D017466:Receptors, Endothelin; D016572:Cyclosporine