DILTIAZEM MODULATES CYCLOSPORINE-A-INDUCED RENAL HEMODYNAMIC-EFFECTS BUT NOT ITS EFFECT ON PLASMA ENDOTHELIN-1

Cyclosporin A (CsA) has been reported to induce major acute renal hypo perfusion that may be antagonised by calcium channel blockers. The vas oconstrictive peptide endothelin-1 (ET-1) has been proposed as a media tor of CsA induced hypoperfusion. We investigated the acute effects of the new CsA formulation (Sandimmun Neoral(R)) in 8 renal transplant p atients on triple immunosuppressive therapy before and following slow- release diltiazem treatment in a dose of 90- 120 mg b.i.d for 4 weeks. CsA significantly increased mean arterial blood pressure by 6 +/- 2 m mHg (p < 0.05) during the first 3 h after administration. This effect was abolished by diltiazem treatment, also reducing blood pressure by 12 +/- 3 mmHg (p < 0.05) 3-9 h after administration. CsA administratio n induced a maximum reduction in renal blood flow of 20 +/- 8% (p < 0. 05) 5 h after ingestion and a concomitant reduction in glomerular filt ration rate of 18 +/- 7% (p < 0.05). The filtration fraction increased by a maximum of 13 +/- 7% (p < 0.05) after 4 h as did the calculated fractional proximal reabsorption by 14 +/- 4% (p < 0.05). All these ac ute renal effects were abolished by diltiazem administration. Concurre nt with the maximum renal hemodynamic effects, plasma ET-1 was elevate d with a peak increase of about 40% 4-5 h after CsA ingestion, Diltiaz em treatment had no effect on the increase in plasma ET-1 following Cs A administration. These findings suggest that CsA induced acute vasoco nstriction and renal hypoperfusion are mediated by ET-1 and that dilti azem treatment abolishes these pharmacodynamic effects of CsA despite persistent increase of plasma ET-1 levels.