The international standard for atrial natriuretic factor. Calibration by an international collaborative study

Atrial natriuretic peptide during human pregnancy and puerperium

In 1981 De Bold and colleagues demonstrated that when extracts of atrial tissue were given intravenously to rats a large diuresis and natriuresis occured promptly. The structure of the hormone concerned, atrial natriuretic peptide (ANP), was elucidated in 1983. Since then, ANP has received attention as a potentially important mediator in the homoeostasis of sodium and fluid volume.

Biodegradable poly(D,L-lactic acid)-poly(ethylene glycol)-monomethyl ether diblock copolymers: structures and surface properties relevant to their use as biomaterials

To obtain biodegradable polymers with variable surface properties for tissue culture applications, poly(ethylene glycol) blocks were attached to poly(lactic acid) blocks in a variety of combinations. The resulting poly(D,L-lactic acid)-poly(ethylene glycol)-monomethyl ether (Me.PEG-PLA) diblock copolymers were subject to comprehensive investigations concerning their bulk microstructure and surface properties to evaluate their suitability for drug delivery applications as well as for the manufacture of scaffolds in tissue engineering. Results obtained from 1H-NMR, gel permeation chromatography, wide angle X-ray diffraction and modulated differential scanning calorimetry revealed that the polymer bulk microstructure contains poly(ethylene glycol)-monomethyl ether (Me.PEG) domains segregated from poly(D,L-lactic acid) (PLA) domains varying with the composition of the diblock copolymers. Analysis of the surface of polymer films with atomic force microscopy and X-ray photoelectron spectroscopy indicated that there is a variable amount of Me.PEG chains present on the polymer surface, depending on the polymer composition. It could be shown that the presence of Me.PEG chains in the polymer surface had a suppressive effect on the adsorption of two model peptides (salmon calcitonin and human atrial natriuretic peptide). The possibility to modify polymer bulk microstructure as well as surface properties by variation of the copolymer composition is a prerequisite for their efficient use in the fields of drug delivery and tissue engineering.

Volemic status influences the response of plasma atrial natriuretic factor to positive airway pressure

STUDY OBJECTIVE; To evaluate interactive effects of volemic status and positive end-expiratory pressure (PEEP) on the plasma levels of atrial natriuretic factor (ANF) in assist-controlled mechanical ventilation (MV).

DESIGN

Three successive protocols applied in randomized order to each participant.

SETTING

Clinical investigation laboratory.

PARTICIPANTS

Twenty-one young, healthy adults.

INTERVENTIONS

The three protocols were as follows: (1) MV+PEEP, normovolemia; (2) MV+PEEP, hypervolemia; and (3) spontaneous breathing (SB), hypervolemia. In protocols 1 and 2, a preliminary period of SB lasting 2 h was followed by MV alone (0.5 h), MV+20 cm H2O PEEP (1 h), and a recovery period of SB (1.5 h). Hypervolemia was induced by the continuous i.v. infusion of 3 L of 0.9% NaCl in 5 h (protocols 2 and 3).

MEASUREMENTS AND RESULTS

Heart rate, BP, and the plasma levels of immunoreactive ANF and catecholamines were measured serially. During hypervolemia, ANF significantly decreased when PEEP was added to MV (protocol 2: from 31.1 +/- 2.7 to 20.7 +/- 1.5 fmol/mL; p < 0.01). This did not occur in normovolemia (protocol 1: from 20.0 +/- to 16.7 +/- 1.2 fmol/mL; p = NS). The different effects of MV+PEEP in normovolemia and hypervolemia were not related to differences in circulating catecholamine levels.

CONCLUSIONS

These results demonstrate for the first time (to our knowledge) that volemic status modulates the response of plasma ANF to PEEP in humans. The role of ANF in the water and salt retention induced by MV with PEEP might be limited to hypervolemic conditions.

Radio-immunoassay of atrial natriuretic peptide (ANP) and characterization of ANP immunoreactivity in human plasma and atrial tissue

A sensitive radio-immunoassay (RIA) was developed to determine the occurrence of atrial natriuretic peptide (ANP) in plasma and atrial extracts from patients undergoing open heart surgery. The immunoreactive ANP (irANP) was characterized by high-pressure liquid chromatography coupled with RIA. The plasma irANP response to releasing stimuli during the operation was determined in simultaneously sampled venous and arterial blood, in order to evaluate any differences. The antiserum recognized the intact ring-structure of alpha-humanANP (alpha-hANP) and its propeptide gamma-hANP, as well as beta-hANP, an anti-parallel dimer of alpha-hANP. Less bioactive N-or C-terminal fragments of alpha-hANP, or an N-terminal fragment of the propeptide, gamma-hANP 1-67, did not cross-react with the antiserum. Sep Pak C18-extraction of plasma resulted in an 80% recovery of synthetic alpha-hANP. The assay had a sensitivity of 1.9 pmol l-1, well below the venous plasma concentrations of irANP found in healthy volunteers (7.4 +/- 1.3 pmol l-1, mean +/- SEM, n = 19), and the local standard was identical to an international standard of alpha-hANP. In atrial extracts three major peaks of irANP were identified as alpha-, beta- and gamma-hANP, with gamma-hANP as the most abundant form. In plasma alpha-hANP dominated, but in two cases high plasma levels of beta-hANP were seen, reflecting the high atrial content in these patients. In peripheral arterial blood, irANP was on an average 56% +/- 20% (p less than 0.01, n = 18) higher than in venous blood; this was associated with more distinct arterial irANP responses to releasing stimuli during the operation.

Kinetics of atrial natriuretic peptide in young and elderly subjects

To study the influence of age on the kinetics of atrial natriuretic peptide (ANP) in man, human (99-126) ANP 2.0 micrograms.min-1 was infused IV for 60 min in 8 healthy young (18 to 25 y) and 9 healthy elderly (71 to 84 y) subjects. Both baseline ANP values and the levels at the end of infusion were higher in the elderly subjects. The mean residence time of ANP in the two age groups was not significantly different, whereas total body clearance (CL) was markedly diminished in the elderly as compared to the young subjects (mean +/- SD 3.1 +/- 1.0 l.min-1 and 6.2 +/- 4.1 l.min-1, respectively). The apparent volume of distribution at steady state was lower in the elderly than in the young, but the difference was not significant (mean +/- SD 44 +/- 19 and 103 +/- 111, respectively. The decrease in CL largely explained the higher ANP levels found in the elderly subjects. The MRT and the plasma half-life of the terminal phase did not differ between the two groups. In the elderly but not in the young subjects the calculated endogenous creatinine clearance was closely correlated with the CL (r = 0.90, P less than 0.001), thereby emphasizing the importance of the kidney in the metabolic clearance of ANP in the elderly.

Comparison of different standards used in radioimmunoassay for atrial natriuretic factor (ANF)

Six different standards for determination of atrial natriuretic factor (ANF) in human plasma samples have been compared using our radio-immunoassay for ANF: International standard 85/669, National Biological Standard Boards, UK; Bachem standard, Torrance, USA; Bachem standard, Bubendorf, Switzerland; Bissendorf standard, Wedemark, Germany; Peninsula standard, Belmont, USA; UCB-Bioproducts standard, Brussels, Belgium. Standard curves obtained with different preparations were in parallel but showed considerable quantitative differences. Standard curves referring to the Bissendorf standard and the International standard, respectively, were almost identical. The dose required for 50% of binding inhibition (ID50s) determined with the Peninsula, UCB and Swiss Bachem standards were higher and ID50 for the American Bachem standard was much lower than ID50 for the International standard. In consequence, estimates of the ANF content in human plasma samples with different standard preparations as the reference showed a considerable variability. With the international standard as the gold reference (plasma ANF concentration 100%) the apparent plasma ANF concentrations measured with the other reference preparations varied from 42% to 178%.

Atrial natriuretic peptide after myocardial infarction

Plasma concentrations of atrial natriuretic peptide (ANP) after acute myocardial infarction were measured at fixed times during 48 hours in 38 patients admitted to the hospital within 4.4 hours after the onset of symptoms. Three hours after admission, the mean concentration of ANP was significantly lower than that at the time of admission. Thereafter it rose steadily until 15 hours after admission. ANP concentrations measured in each patient at the time of admission and the individual mean ANP concentrations during the first 48 hours after admission correlated weakly but significantly with the size of the infarct and the left ventricular function. Neither the site of the infarct, the occurrence of reperfusion, nor the number of coronary vessels affected influenced the ANP concentration. In 24 patients in whom cardiac catheterization was performed, no relationship between ANP concentrations and left ventricular pressures was observed. Determination of ANP concentrations seems to be of little value in assessing cardiac function after acute myocardial infarction.