Treatment with
aprotinin, a broad-spectrum
serine protease inhibitor with a molecular weight of 6512 Da, was associated with
acute kidney injury, which was one of the reasons for withdrawal from the market in 2007. Inhibition of renal
serine proteases regulating the
epithelial sodium channel ENaC could be a possible mechanism. Herein, we studied the effect of
aprotinin in wild-type 129S1/SvImJ mice on
sodium handling, tubular function, and integrity under a control and
low-salt diet. Mice were studied in metabolic cages, and
aprotinin was delivered by subcutaneously implanted sustained release pellets (2 mg/day over 10 days). Mean urinary
aprotinin concentration ranged between 642 ± 135 (day 2) and 127 ± 16 (day 8) µg/mL .
Aprotinin caused impaired
sodium preservation under a
low-salt diet while stimulating excessive
hyperaldosteronism and unexpectedly, proteolytic activation of ENaC.
Aprotinin inhibited proximal tubular function leading to glucosuria and
proteinuria. Plasma
urea and
cystatin C concentration increased significantly under
aprotinin treatment. Kidney tissues from
aprotinin-treated mice showed accumulation of intracellular
aprotinin and expression of the kidney injury molecule 1 (KIM-1). In electron microscopy, electron-dense deposits were observed. There was no evidence for kidney injury in mice treated with a lower
aprotinin dose (0.5 mg/day). In conclusion, high doses of
aprotinin exert nephrotoxic effects by accumulation in the tubular system of healthy mice, leading to inhibition of proximal tubular function and counterregulatory stimulation of ENaC-mediated
sodium transport.