Abstract 210: Urinary Renin as a New Marker of Preeclampsia?
Urinary renin-angiotensin system (RAS) components have been suggested to reflect intrarenal RAS activity. Urinary renin is elevated in diabetes, thus explaining the effectiveness of RAS blockade in diabetic nephropathy despite the low-to-normal plasma renin levels in this condition. Here we investigated urinary renin levels in preeclampsia (PE), a disease characterized by hypertension and proteinuria. We speculated that urinary renin levels might be of additional value on top of the elevated sFlt-1/PlGF ratio in PE. Renin, prorenin, creatinine (Cr), total protein, s-Flt-1 and PlGF were determined in plasma (15 PE, 6 non-PE) and/or 24 hour-urine samples (39 PE, 27 non-PE) of pregnant women. Gestational age was 33±1 in PE vs. 37±0 weeks in non-PE. The sFlt-1/PlGF ratio (523 (30-49996) vs. 10 (2.9-32.5)) (geometric mean and range) was higher in PE vs. non-PE. Plasma renin and prorenin levels in PE were 42 (range 11-181) and 190 (95-274) ng/L, versus 41 (16-80) ng/L and 129 (87-160) ng/L in non-PE. Plasma total protein levels in PE and non-PE were 50 (21-68) and 61 (58-66) g/L, resp., versus 1.0 (0.3-13) and 0.2 (0.1-1.5) g/L in urine. Plasma Cr levels in PE and non-PE were 61 (39-110) and 61 (47-83) μmol/L, resp., versus 31 (2.6-241) and 11 (3.4-56) mmol/L in urine. Urinary renin levels were ≈3 times higher in PE than in non-PE (3.2 (0.1-410) vs. 1.4 (0.3-13.0) ng/L), and 5-10 times higher than expected if filtration of plasma renin paralleled filtration of plasma protein. In contrast, urinary prorenin levels were 0.4 (0.1-84) and 0.1 (0.1-0.9) ng/L in PE and non-PE, i.e., as high as expected on the basis of plasma protein filtration. In line with these observations, urinary total protein and Cr correlated with urinary prorenin (r=0.38, P<0.05 and r=0.71, P<0.01, resp.), but not with urinary renin. In conclusion, urinary prorenin levels run in parallel with urinary total protein and Cr levels, and are as high as can be expected based upon protein filtration in the kidney. In contrast, urinary renin levels are 5-10 fold higher than expected based on filtration, and do not correlate with urinary protein or Cr. Urinary renin may therefore reflect an activation of the renal RAS in PE, and could serve as a new marker of the severity of this disease, in particular its renal consequences.
- © 2012 by American Heart Association, Inc.