Identification and Plasma Concentrations of the N-Terminal Fragment of Proatrial Natriuretic Factor in Man*

Abstract

A specific RIA was developed to measure plasma atrial natriuretic factor (ANF) N-terminal immunoreactivity in man. Antibodies raised in rabbits against a rat ANF N-terminal fragment [ANF-(11-37)] had 100% cross-reactivity with human ANF-(1-30) and purified plasma N-terminal ANF immunoreactivity. The ED80 and ED50 of standard curves prepared using [125I]human ANF-(1-30) and human ANF-(1-30) were 31.5 +/- 5.4 (+/- SD) and 132.5 +/- 20.4 fmol/tube, respectively. The plasma ANF N-terminal peptide concentrations were assayed directly, without extraction, since dilution of plasma and addition of standard to plasma yielded parallel dose-responses in the RIA and virtually 100% recovery of ANF-(1-30) added to plasma. Purification of ANF N-terminal immunoreactivity from 1.5 L human plasma by affinity chromatography and amino acid sequencing suggested that it was closely related to ANF-(1-98), although some degraded peptides were also detected. The mean basal plasma ANF N-terminal peptide level measured in 34 normal subjects was 420 +/- 157 (+/- SD) pmol/L. The values were higher in plasma from patients with congestive heart failure (grades III and IV; 7,041 +/- 6,136 pmol/L; n = 13) or chronic renal failure (10,079 +/- 4,942 pmol/L; n = 20). In 9 patients with chronic renal failure, hemodialysis resulted in a 30% (P less than 0.05) decrease in plasma ANF-(99-126) levels, from 34.7 +/- 12.3 (+/- SD) to 23.2 + 6.1 pmol/L, but no changes in plasma ANF N-terminal peptide concentrations. These data indicate that the N-terminal portion of pro-ANF is cosecreted with ANF-(99-126). Its higher plasma levels in the basal state and during chronic renal failure suggest a different process of elimination than that of ANF-(99-126), which may be partly mediated by the kidney.

The effect of aortic valve replacement on N‐terminal natriuretic propeptides in patients with aortic stenosis

“…The plasma NT-proANP (irANP 1-98) concentration was measured in unextracted plasma according to Sundsfjord et al 11 The detection limit for NT-proANP was 185 pmol/l and the between and within assay coefficients of variation were 4.1 and 6.3%, respectively. Recovery was 85% (n = 10).…”

Different behaviour of the N-terminal and C-terminal fragment of proatrial natriuretic factor in plasma of healthy subjects as well as of patients with cirrhosis

“…Another explanation for increased NTA at normal CTA concentrations could be an impaired elimination of the /V-terminal fragment in cirrhosis. Renal elimination of NTA has been suggested, based on the observation of more marked elevations of NTA than of CTA in patients with chronic renal failure [4]. In the cirrhotic patients of this study, normal serum creatinine levels make significant renal impairment rather unlikely.…”

Water immersion increases the concentration of the immunoreactive N-terminal fragment of proatrial natriuretic factor in human plasma

“…Upon appropriate stimulation,such as atrial stretch (2), it is released and cleaved, and in the plasma the biologically active form has been identified as the 28 amino acid C-terminal fragment ANF 99-126 (3-7). Recently,presence of the N-terminal fragment ANF 1-98 has also been demonstrated in plasma of both,rat and man (8,9). This finding together with the observation of increased …”

“…The RIA procedure for the N-terminal fragment with antibody GT 23 has been reported elsewhere in detail (9). …”