Renal hemodynamics and renoprotection

Background: Angiotensin II (AII) is the well-known determinant of kidney damage increasing intraglomerular pressure, matrix expansion and fibroblast proliferation. Renin-angiotensin system (RAS) inhibition, limiting the hemodynamic effects of AII, reduces proteinuria and is renoprotective in the long term. Methods: We studied 15 chronic proteinuric patients by Doppler ultrasonography to clarify the intrarenal hemodynamic changes during RAS blockade by Benazepril (10-20 mg/day) alone and combined with Valsartan (80-160 mg/day). We also investigated the correlation between hemodynamic indices, RAS components and antiproteinuric effect. Results: After 1 month of Benazepril proteinuria, resistive index (RI) and pulsatility index (PI) significantly decreased and proteinuria reduction was directly correlated to decrease in RI (r = 0.55, p = 0.03). Contrarily, after 1 month of combined therapy, RI and PI restored to baseline and progressively increased in the following 3 months, while proteinuria decreased. Increase in RI was directly correlated to concomitant increase in plasma renin activity (r = 0.65, p = 0.01) suggesting a direct role of renin in restoring intrarenal resistances. Conclusion: The hemodynamic changes caused by RAS inhibitors partially contribute to the antiproteinuric effect. Other RAS components, such as renin, may contribute to renal vasoconstriction and could be a further determinant of kidney damage besides a promising target for renoprotection. Copyright (C) 2008 S. Karger AG, Basel