A single heterozygous nucleotide substitution displays two different altered mechanisms in the FBN1 gene of five Italian Marfan patients.

The Fibrillin-1 gene (FBN1; chromosome 15q21.1) encodes a major glycoprotein component of the extracellular matrix. Mutations in FBN1, TGFBR1, TGFBR2 are known to cause Marfan syndrome (MIM 154700), a pleiotropic disorder. In the present study, we describe five novel missense FBN1 mutations in five Marfan patients that have the peculiarity to activate two contemporary mutational mechanisms: a missense mutation and exon skipping.

Systemic hemodynamics and renal function during brain natriuretic peptide infusion in patients with essential hypertension.

We assessed the cardiovascular and renal effects of human brain natriuretic peptide (BNP) infused at a dose inducing an increase in plasma BNP to pathophysiologic levels, in eight hypertensive patients in a randomized, placebo-controlled, cross-over study. Left ventricular performance, cardiac output (echocardiography), heart rate, arterial pressure, glomerular filtration rate (GFR; creatinine clearance), sodium excretion, intrarenal sodium handling (lithium clearance method), and urine flow rate were measured in the infusion and postinfusion periods (1 h each), together with plasma BNP and the urinary excretion rate of cGMP. Plasma BNP levels increased from 2.90 +/- 0.74 to 36.43 +/- 5.51 pmol/L (P < .01) at the end of the infusion and were still elevated at the end of the postinfusion period (7.03 +/- 1.41 pmol/L, P < .05). The urinary excretion of cGMP was also significantly higher during BNP infusion. Left ventricular performance, cardiac output, arterial pressure, and peripheral vascular resistance were not affected by BNP. Peptide infusion induced a significant increase in GFR (placebo, 115 +/- 24; BNP, 147 +/- 19 mL/min), sodium excretion (placebo, 129 +/- 40; BNP, 243 +/- 60 mumol/min), and urine flow rate. All these effects were observed also in the postinfusion period. The natriuretic effect of BNP was attributable to both an increase in filtered sodium load and a reduction of distal sodium reabsorption. These results suggest that BNP may contribute to maintain renal function and sodium excretion in patients with essential hypertension.

Plasma levels of natriuretic peptides during ventricular pacing in patients with a dual chamber pacemaker.

The mechanism(s) responsible for the release of brain natriuretic peptide (BNP), a cardiac hormone of ventricular origin, are still not completely understood. We measured plasma atrial natriuretic peptide (ANP) and BNP in 15 subjects (10 men, mean age 67 +/- 3 years) with a dual chamber pacemaker and unimpaired heart function during ventricular pacing, which is known to induce an increase in atrial pressure and plasma ANP concentration. Under ECG monitoring, all subjects received sequential atrioventricular pacing for 30 minutes and ventricular pacing for 30 minutes, at the same rate of 80 beats/min. Arterial pressure and plasma BNP and ANP levels were measured every 10 minutes throughout the study. Ventricular pacing led to atrioventricular dissociation in eight subjects and to retrograde ventriculo-atrial conduction in seven. Arterial pressure remained unchanged in all subjects. In the group with atrioventricular dissociation, plasma ANP increased from 10.14 +/- 0.58 to 16.72 +/- 0.92 fmol/mL at the 60th minute (P < 0.0001), whereas plasma BNP did not change at all (from 1.26 +/- 0.07 to 1.16 +/- 0.09 fmol/mL). In the group with retrograde conduction, plasma ANP concentration doubled (from 10.95 +/- 1.66 to 21.40 +/- 1.51 fmol/mL, P < 0.0001), BNP increased 1.5-fold (from 1.16 +/- 0.06 to 1.64 +/- 0.14 fmol/mL, P < 0.001), and the ANP:BNP ratio augmented from 10:1 to 13.4:1. These results indicate that the release of ANP and BNP is regulated by different mechanisms, supporting the view that there is a dual natriuretic peptide system, comprising ANP from the atria and BNP from the ventricles.

Cardiovascular and renal effects of low dose brain natriuretic peptide infusion in man.

We evaluated the effects of pathophysiological levels of human brain natriuretic peptide (BNP), a recently identified cardiac hormone with natriuretic activity, by determining the hemodynamic and renal responses to low dose infusion (4 pmol/kg.min for 1 h, from 1500-1600 h) of human synthetic BNP in five healthy volunteers in a randomized placebo-controlled crossover study. Compared to placebo, BNP induced significant increases in effective renal plasma flow (para-aminohippurate clearance), glomerular filtration rate (creatinine clearance), urine flow rate, and sodium excretion without affecting blood pressure, heart rate, cardiac output (echocardiographic method), peripheral vascular resistance, PRA, plasma aldosterone, or plasma norepinephrine to any significant extent. Exploration of segmental sodium handling by the lithium clearance technique showed that the natriuretic effect of BNP was due to both an increase in filtered sodium load and a reduced distal sodium reabsorption. These results indicate that the high plasma BNP levels observed in disease states, such as heart failure, may contribute to the regulation of renal hemodynamics and sodium excretion.