Pathways of glomerular toxicity of cyclosporine-A: An "in vitro" study

Background/Aims. Knowledge of renal toxicity of cyclosporine-A (CyA) is clouded by multiple effects on different glomerular and tubular cells and on kidney and systemic hemodynamics. To focus on glomerular action of CyA we used glomeruli isolated in vitro, with the aim of dissecting the effects on recruitment of glomerular vasoconstricting systems, like endothelin-1 (ET) and angiotensins (AI and AII). Methods. We studied the pathways of CyA damage on pig glomeruli isolated in vitro with the technique of sieving through mesh filters of different sizes, and incubated in an appropriate culture medium. The supernatant was sampled at different time intervals to measure ET, AI and AII concentrations upon addition of ET 10^-12 or CyA 4.10^-7 M, with or without either selective endothelin receptor A (ET_A) or B (ET_B), or unselective ET_A-ET_B receptor inhibitors. Results. CyA increased ET concentration (from 9.7±0.3 to 11.4±0.4 pg·ml^-1, p<0.002), and the added ET released AI in the medium (from 26.6±4.7 to 39.1±4.6 pg·ml^-1, p<0.05) when ET_B receptors were blocked. In contrast, CyA stimulated angiotensins release independent of ET receptors blockade, hence, irrespective of ET concentration in the medium, from 26.6±4.7 to 38.0±2.1 pg·ml^-1 for AI, p<0.05, and from 12.3±1.0 to 14.8±0.9 pg·ml^-1 for AII, p<0.05. Conclusion. CyA releases ET and angiotensins independently by a direct action. Glomerular CyA toxicity might be mediated by recruitment of vasoconstricting peptides and modulated by relative ET_A and ET _B receptor occupancy.