Structural and functional features of atrial natriuretic peptides

Plasma atrial natriuretic polypeptide in the elderly: age or hypertension?

The effect of age and raised blood pressure on the plasma concentration of atrial natriuretic peptide (ANP) was examined in 20 young (23-49 years), 20 elderly normotensive (71-80 years) and 20 elderly hypertensive (71-82 years, BP > 160/90 mmHg) individuals. Median plasma ANP was 27.6 pg/ml (range, 16.8-94.0 pg/ml) in the young group; 62.0 pg/ml (range, 28.6-124.3 pg/ml) in the elderly normotensive and 74.4 pg/ml (range,25.2-423.6 pg/ml) in the elderly hypertensive group. Plasma ANP rose significantly with age, but there was no difference between elderly normotensive and hypertensive groups.

Atrial natriuretic peptide in human plasma--comparison of radioreceptor versus radioimmunoassay

A sensitive and specific procedure for the measurement of atrial natriuretic peptide (ANP) in human plasma by radioreceptor assay, using bovine adrenal membranes treated with Triton-X-100, is described. Plasma levels (mean +/- SEM) of ANP in healthy subjects on a normal sodium intake were 8.4 +/- 1.4 pg/ml and could be modified by changes in sodium intake with increases in sodium intake being associated with higher levels. Mean plasma ANP was approximately 2-fold higher in patients with essential hypertension and 4-fold higher in patients with cardiac or renal disease. The values obtained were comparable in magnitude to those obtained by radioimmunoassay and there was a strong correlation (r = 0.94; p less than 0.001) between the values obtained by radioimmuno- and radioreceptor-assay. These results suggest that circulating ANP corresponds to the biologically active peptide and point to an important role of the atrial peptides in the control of sodium balance.

Divergence of ANF analogs in smooth muscle cell cGMP response and aorta vasorelaxation: evidence for receptor subtypes

ANF analog potencies in stimulating smooth muscle cell cGMP were compared with the ability to relax histamine-constricted rabbit aorta in vitro. ANF[1-28], [5-28], [5-27] and Lys-11[5-28] elevated cGMP and were potent vasorelaxants. ANF[7-23] and Lys-11[7-23] were potent cGMP stimulators but 1000-fold weaker relaxants. Tyr-8[5-27] did not stimulate cGMP synthesis or antagonize the response of the other peptides, yet was a potent vasorelaxant. Crosslinking with 125I-ANF identified bands at 150 and 65 KD by SDS-PAGE. ANF[1-28], Lys-11[7-23] and Tyr-8[5-27] blocked crosslinking at low concentration despite disparate activities. These data support the existence of ANF receptor subtypes and suggest that cGMP elevation alone is not sufficient to promote atrial peptide-induced vasorelaxation.