Cyclosporine impairs the guanylyl cyclase activity of the natriuretic peptide receptor in the glomerulus

Human B-natriuretic peptide improves hemodynamics and renal function in heart transplant patients immediately after surgery

BACKGROUND

B-natriuretic peptide (BNP) is effective in the treatment of decompensated heart failure, but has not specifically been evaluated in the immediate postoperative cardiac transplant population.

OBJECTIVE

To determine if BNP can favorably alter hemodynamics in the perioperative setting after heart transplantation.

METHODS AND RESULTS

We administered (human)BNP ((h)BNP, Nesiritide) to 10 consecutive patients with preexisting renal insufficiency and elevated filling pressures. All patients had failed to respond to inotropes and escalating doses of diuretics. BNP was started 48 hours after transplantation, and continued for 48 to 72 hours. Intravascular hemodynamics were measured. With (h)BNP therapy, the pulmonary capillary wedge pressure, central venous pressure, and mean pulmonary artery pressure were all attenuated, whereas the cardiac output was significantly increased. The mean urine output increased significantly in the first 24 hours of therapy with no increase in diuretics. Implementation of BNP therapy allowed for a reduction of patients' inotropes and diuretics, while decreasing serum BNP levels.

CONCLUSION

An improvement in cardiac hemodynamics and renal function was observed with administration of (h)BNP in these postsurgical patients with elevated filling pressures and acute on chronic renal insufficiency. This study demonstrates that posttransplant patients retain the capacity to respond to exogenous BNP immediately after surgery.

Augmented natriuretic peptide-induced guanylyl cyclase activity and vasodilation in experimental hyperglycemic rats

The present study was aimed to investigate whether hyperglycemia may alter the regulation of vascular natriuretic peptide receptors (NPR). The hyperglycemia was induced in rats by the treatment with streptozotocin (50 mg/kg, i.v.). The expression of different subtypes of NPR was determined in the thoracic aorta by reverse transcriptase-polymerase chain reaction and quantitative in vitro receptor autoradiography. The isometric tension and the guanylyl cyclase activity of the isolated thoracic aorta in response to natriuretic peptides were also determined. Following the treatment with streptozotocin, the plasma concentration of atrial natriuretic peptide (ANP) was significantly increased. The expression of NPR-A was increased, while that of NPR-C was reduced. The receptor binding study demonstrated an increased maximal binding capacity of NPR, with its affinity not significantly altered. The magnitude of vasodilation and guanylyl cyclase activity in response to ANP was significantly increased. On the other hand, the vasodilator response as well as the tissue formation of cGMP in response to acetylcholine or sodium nitroprusside was significantly reduced. These results indicate that the hyperglycemia may cause an altered regulation of vascular NPR.