Immunoreactive N-terminal fragment of proatrial natriuretic peptide, ANP (1-98), in plasma of healthy dogs and dogs with impaired volume regulation: a comparison with the C-terminal ANP (99-126).

Atrial natriuretic peptide (ANP) is stored in atrial myocytes as a 126 amino acid precursor molecule (ANP 1-126) and is cleaved during its release into circulation into the biologically active C-terminal ANP (99-126) and the N-terminal counterpart, ANP (1-98). While interest has focused on ANP (99-126) under physiological and pathophysiological conditions, data for the cosecreted N-terminal sequence, ANP (1-98) are generally missing. Plasma levels of the N-terminal immunoreactive peptide (N-ANP [1-98]) were measured in normal dogs, and in dogs with impaired volume regulation (congestive heart failure; chronic renal failure or Cushing's syndrome and compared with those of C-ANP (99-126). The N-ANP (1-98) concentration was 593.1 +/- 81.1 fmol ml-1 in normal subjects, which is about 60-fold higher than the C-ANP (99-126) (10.8 +/- 2.6 fmol ml-1). In patients suffering from chronic renal failure ANP (1-98) was increased to 1582 +/- 196 fmol ml-1, and in dogs with congestive heart failure to 1612 +/- 244 fmol ml-1. In contrast, Cushing's syndrome dogs showed decreased N-ANP (1-98) concentrations (351 +/- 65.9 fmol ml-1). There was a positive correlation between plasma levels of N-ANP (1-98) and C-ANP (99-126) levels (correlation coefficients: normal: r = 0.78; congestive heart failure: r = 0.76; chronic renal failure: r = 0.86; Cushing's syndrome: r = 0.57). High pressure liquid chromatographic analysis of dog plasma showed one major peak of N-terminal immunoreactivity corresponding to ANP (1-98).(ABSTRACT TRUNCATED AT 250 WORDS)