Site specific regulation in the kidney of endothelin and its receptor subtypes by cyclosporine.

Endothelin (Et) has been suggested by us and others to play a role in glomerular dysfunction that characterizes cyclosporine (Cs)-associated nephrotoxicity. Since Et exerts its actions through at least two receptor subtypes, and because these receptor subtypes have particular distributions in the renal parenchyma, we investigated changes in mRNA expression for Et and its receptor subtypes in glomeruli and medulla of rats treated with Cs. Polymerase chain reaction coupled with reverse transcription (RT-PCR) method was used to assess prepro-Et-1, type A (EtA) and type B (EtB) receptor mRNA at 1, 3, 6, and 24 hours after Cs (20 mg/kg body wt i.v.). Results were normalized to the expression of beta-actin as an internal standard. Compared with control rats, glomerular mRNA expression for prepro-Et-1 was not affected by Cs. Similarly, Cs did not significantly change the glomerular mRNA expression of either EtA or EtB receptor subtypes. By contrast, in the medulla there was a marked and persistent increase in the expression for prepro-Et-1 and the EtB receptor subtype: prepro-Et-1 at 1, 3, 6, and 24 hours was 336 +/- 61, 295 +/- 65, 339 +/- 73, 440 +/- 123% of controls, respectively (P < 0.05 compared with controls at each time point). The EtB receptor mRNA at 1, 3, 6, 24 hours was 164 +/- 22, 157 +/- 15, 148 +/- 14, 116 +/- 18% (compared with controls, P < 0.01 at 3 hr and P < 0.05 at 1 and 6 hr), while the mRNA expression for EtA was not affected by Cs treatment.(ABSTRACT TRUNCATED AT 250 WORDS)