Demonstration and characterization of α‐human atrial natriuretic factor in human plasma

Abstract

This paper describes a highly specific and sensitive radioimmunoassay for a-human atrial natriuretic factor (a-hANF), the C-terminal 28-amino-acid residue portion of human prepro-ANF in human plasma. A novel extraction and prepurification procedure allowed for detection of levels of immunoreactive-a-hANF as low as 0.5 fmol/ml. In normotensive subjects, levels in the range l-23 fmol/ml (mean = 8.9 fmol/ml) were found. Combined gel permeation and HPLC analysis demonstrated that this ir-a-hANF was comprised virtually exclusively of authentic 28-residue a-hANF. No evidence for occurrence of larger precursor forms in human plasma was acquired. A heterogenous group of hypertensive patients displayed considerably higher levels (mean = 62.2 fmol/ml), of interest in view of the hypotensive properties of ANF.

α‐h‐ANP is the only form of circulating ANP in humans

“…The moab shows complete crossreactivity with rat ANP I, II, and III, rat ANP (1-28) and human ANP fragment (7-28) while there is no inhibition of 125I-ANP binding by rat ANP fragments (13-28), (18-28) and (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11) (fig. 1).…”

“…The predominant lowMr species purified from human atrial is o~-human ANP (ot-h-ANP). So far there exists only indirect evidence as to whether this is the only circulating form of ANP [8][9][10][11]. Here, we describe the purification of atrial peptides from human plasma by immunoaffinity chromatography and reversedphase HPLC.…”

Presence of the atrial natriuretic factor (ANF) in human ascitic fluid

“…Extraction procedures as well as characteristics of our highly sensitive and specific radioimmunoassay for determination of ANF in plasma have been previously described (6,9). Application of the extraction proce dure to aliquots of ascitic fluid yielded high recovery rates, not different from those obtained in plasma.…”

“…This might be due to ANF re lease stimulated by the hemodynamic changes following ascites infusion or due to elevated ANF concentrations in ascitic fluid. Whereas the presence of atrial natriuretic factor (ANF) has been demonstrated in various fluids of the human body, such as plasma (6), urine (7) and cerebrospinal fluid (8), ascitic fluid has not been examined as yet for the occurence of ANF.…”

Atrial natriuretic factor

“…the prohormone is stored in secretory vesicles. ANF-126 is further processed enzymatically and secreted into the blood, where the biologically active C-terminal ANF-28 has been defined as the circulating hormone [27,35,36]. Increased dietary sodium intake has been shown to stimulate ANF release [37].…”