BNP and N-terminal proBNP are both extracted in the normal kidney.

BACKGROUND: Increased plasma concentrations of cardiac-derived B-type natriuretic peptide (BNP) and N-terminal pro-B-type natriuretic peptide (proBNP) are both associated with left ventricular dysfunction. Information on the regional elimination of the peptides is, however, still scarce. We therefore examined the renal and peripheral extraction of N-terminal proBNP and BNP.
MATERIALS AND METHODS: The study comprised 18 patients with essential arterial hypertension, 51 with cirrhosis, and 18 control patients without kidney or liver disease. All patients underwent a haemodynamic investigation with catheterization of the femoral artery and femoral and renal veins. Blood sampling from the catheters allowed determination of the arteriovenous extraction ratio of N-terminal proBNP and BNP.
RESULTS: Neither the peripheral N-terminal proBNP (13, 11, 19 pmol L(-1), NS) nor the BNP plasma concentrations (4, 12, 9 pmol L(-1), NS) differed between the patient groups. In addition, similar renal extractions were observed in the groups. The renal extraction of N-terminal proBNP (0.16) was not different from that of BNP (0.16). In contrast, the N-terminal proBNP extraction in the lower extremity was markedly lower compared with BNP (0.00 vs. 0.125, P = 0.007).
CONCLUSIONS: A comparable renal elimination of N-terminal proBNP and BNP is contrasted by a selective extraction of BNP in the lower extremity. Our results suggest a different elimination mechanism in the renal and peripheral circulation, which partly may explain the higher N-terminal proBNP compared with BNP concentrations in normal plasma.