Antiproteinuric effect of ciclosporin A in adriamycin nephropathy in rats

Ciclosporin A (CsA) can reduce proteinuria in various forms of human and experimental glomerulopathies. This antiproteinuric effect can be the result of a decrease of immunological damage, a decrease in the glomerular filtration rate (GFR), or a change in the permselective properties of the glomerular capillary wall. In this study we investigated the effect of CsA on Adriamycin-induced nephropathy in rats. A single intravenous injection of Adriamycin (5 mg/kg body weight) induced a severe nephrotic syndrome with a massive albuminuria (+/- 400 mg/24 h from 3 weeks onwards) and a hypoalbuminemia (+/- 7 mg/ml after 5 weeks). The IgG/albumin selectivity index was 0.16 +/- 0.05, indicating a preferential loss of albumin. A 5-day treatment with CsA reduced the albumin excretion by almost 50% (from 336 +/- 91 to 178 +/- 58 mg/24 h; p = 0.002) and induced an increase in the serum albumin level (from 7.1 +/- 4.1 to 12.8 +/- 3.2 mg/ml; p = 0.002) in contrast to the vehicle olive oil (OO). CsA also decreased the GFR by 40% (from 0.74 +/- 0.11 to 0.41 +/- 0.11 mg/ml/100 g body weight; p = 0.002). Albuminuria corrected for the GFR (fractional excretion of albumin, FE(alb)) was still significantly lower in CsA-treated than in OO-treated animals (FE(alb) CsA: 1.35 +/- 0.88, FE(alb) OO: 3.17 +/- 2.29%; p = 0.0005). This suggests that other factors are also involved in the reduction of albuminuria. To exclude that CsA has an effect on the tubular reabsorption of albumin, we evaluated the blockade of the tubular reabsorption by lysine and found no difference in albuminuria between the CsA- and OO-treated groups. These experiments suggest that the antiproteinuric effect of CsA is not (only) due to a decrease in the GFR, but also to a decrease of the enhanced permeability of the glomerular capillary wall for albumin.