Human atrial natriuretic factor (ANF). Characterisation of a monoclonal antibody panel and its use in radioimmunoassay

Analysis of peptides derived from Pro Atrial Natriuretic Peptide that circulate in man and increase in heart disease

The present investigation was designed to determine the levels and circulating forms of peptides derived from Pro Atrial Natriuretic Peptide (ProANP) and to assess their usefulness as markers for severity of heart disease. A sensitive and specific "two-site" immunoradiometric assay (IRMA) for the measurement of C-terminal ProANP 99-126 (alpha ANP) and two radioimmunoassays (RIAs) for the measurement of N-terminal ProANP 31-67 and ProANP 79-98 were developed. Immunoassays were validated by measurement of circulating peptide concentrations in 15 normal volunteers and 44 patients with varying degrees of heart disease. Mean concentrations of immunoreactive (ir) alpha ANP, ProANP 79-98 and ProANP 31-67 in normal volunteers (n = 15) were 8.5 +/- 1.1, 143 +/- 16 and 587 +/- 83 pmoles/l, respectively, increasing in patients with mild heart disease (NYHA I to II; n = 22) to 17.1 +/- 2.1, 691 +/- 197 and 2160 +/- 540 pmoles/l with greatest increases being observed in patients with severe heart disease (NYHA III to IV; n = 22) of 103 +/- 23, 4550 +/- 590 and 10,600 +/- 1350 pmoles/l, respectively. RP-HPLC of pooled plasma revealed peaks corresponding to alpha ANP, beta ANP, ProANP 1-126, ProANP 1-98, ProANP 31-67 and ProANP 79-98, all apparently increased in heart disease. In conclusion, using a series of immunoassays, we observed the graded increase of alpha ANP, irProANP 31-67 and irProANP 79-98 with increasing severity of heart disease. All peptides proved useful markers, but only ProANP 79-98 levels were able to distinguish patients with mild heart disease (NYHA I) from normals. Finally, RP-HPLC analysis indicated that ProANPs 31-67 and 79-98 circulate as distinct entities, in addition to ProANP 1-98.

Reduced renal hemodynamic response to atrial natriuretic peptide in elderly volunteers

Aging is associated with decreased ability to excrete salt and water, thus increasing the susceptibility to volume overload in older individuals. Meanwhile, plasma levels of atrial natriuretic peptide (ANP) increase progressively with age for unknown reasons. We compared the natriuretic and renal hemodynamic responses to low-dose ANP infusion in an elderly group of volunteers (mean age, 74 years) with those of a group of younger subjects (mean age, 29 years). A significant reduction below baseline values in effective renal plasma flow occurred in the young group after the 2-hour peptide infusion (657 +/- 125 v 476 +/- 92 mL/min [mean +/- 1 SD]) when compared with the elderly group (two-way analysis of variance; P < 0.02). A concomitant increase in renal vascular resistance was noted in the young group only during the same period (6,631 +/- 1,384 v 9,136 +/- 2,126 dyn s cm2 x 10(6)). This increase was also significantly higher than that in the elderly group (analysis of variance; P < 0.02). Both groups demonstrated similar natriuretic responses. Absolute sodium excretion had increased significantly above baseline values in both young and elderly subjects at the end of the 2-hour peptide infusion (111 +/- 25 mumol/min to 183 +/- 33 mumol/min v 107 +/- 23 mumol/min to 198 +/- 56 mumol/min) and remained elevated until 1 hour postinfusion. We conclude that the elderly subjects in our study demonstrated a diminished renal hemodynamic response to infusion of ANP while preserving a natriuretic response similar to that found in the younger subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Radioimmunoassays of arginine vasopressin and atrial natriuretic peptide: application of a common protocol for plasma extraction using Sep-Pak C18 cartridges

A rapid vacuum-driven procedure, using pre-treated Sep-Pak C18 cartridges, has been developed for the simultaneous extraction of arginine vasopressin (AVP) and atrial natriuretic peptide (ANP) from plasma. Non-specific interference was removed by fractional elution with an aqueous methanol/trifluoroacetic acid (TFA) mixture. AVP and ANP were coeluted under positive pressure with a methanol/TFA mixture and the eluates air-dried before measurement using separate radioimmunoassays. Assay ranges for AVP and ANP were 0.12-29.5 pmol/L and 0.65-162 pmol/L, respectively, with mean recoveries (standard deviation in parentheses) for AVP of 96.4% (5.5%) at a level of 11.8 pmol/L and for ANP of 94.8% (5.9%) at a level of 32.4 pmol/L. The extraction and assay procedures were validated by observing the changes in plasma AVP and ANP concentrations in normal subjects at different stages of hydration and in elderly patients during treatment for congestive cardiac failure.

Renal sodium retention does not occur during the luteal phase of the menstrual cycle in normal women

OBJECTIVE

To determine whether weight gain due to renal sodium and water retention occurs in the luteal phase of the normal menstrual cycle.

DESIGN

Prospective observational study.

SETTING

Research laboratory installed with modified spa bath.

SUBJECTS

Ten normal healthy women.

INTERVENTION

Each subject underwent two experiments, one in each phase of the menstrual cycle, involving 3 h head-out water immersion and a pre- and post immersion control hour. 25 ml blood samples were obtained every hour before, during and after water immersion.

MAIN OUTCOME MEASURES

Renal and hormonal responses to water immersion during the luteal and proliferative phases of the cycle.

RESULTS

There was no change in weight, creatinine clearance, basal sodium excretion or plasma atrial natriuretic peptide between the two phases of the cycle. There was a significant rise in basal progesterone, plasma aldosterone and plasma renin activity in the luteal phase of the ovulatory cycles. Renal and hormonal responses to immersion including sodium and calcium excretion, elevation of atrial natriuretic peptide (ANP) and suppression of plasma aldosterone and plasma renin activity were identical in the two phases of the menstrual cycle.

CONCLUSION

We found no evidence to support the hypothesis that renal sodium and water retention occurs in the luteal phase of the normal menstrual cycle.