We designed the present study to assess any changes in plasma concentrations of the novel vasorelaxant peptide adrenomedullin in patients with essential hypertension. Plasma adrenomedullin concentrations were measured in 45 patients with untreated essential hypertension, 15 patients with borderline hypertension, and 30 normotensive control subjects. After 4 weeks of effective calcium channel blocker-based antihypertensive therapy, adrenomedullin concentrations were measured again. The concentrations were higher in hypertensive patients with increased serum creatinine levels or decreased glomerular filtration rates compared with borderline hypertensive patients and normotensive subjects, although values in normotensive and hypertensive individuals overlapped. Plasma adrenomedullin concentrations were positively correlated with serum creatinine levels and inversely correlated with glomerular filtration rates in the hypertensive patients, whereas adrenomedullin values were not correlated with blood pressure level, left ventricular mass index, or left ventricular ejection fraction. Despite blood pressure control with antihypertensive therapy, plasma adrenomedullin concentrations were not changed. Reversed-phase high-performance liquid chromatographic analysis showed that a major component of immunoreactive adrenomedullin in the plasma of normotensive subjects and hypertensive patients is human adrenomedullin-(1-52). These results indicate that plasma adrenomedullin concentrations are elevated in many hypertensive patients with renal dysfunction and its major component is human adrenomedullin-(1-52).

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The present study investigated the effect of adrenomedullin, a novel vasorelaxant peptide, on the migration of cultured rat vascular smooth muscle cells (SMCs) by using the Boyden-chamber method. Fetal calf serum (FCS) and platelet-derived growth factor (PDGF)-BB strongly stimulated SMC migration. Adrenomedullin clearly inhibited SMC migration stimulated with 5% and 10% FCS in a concentration-dependent manner. The migration induced by 10 and 25 ng/mL PDGF-BB was also inhibited by adrenomedullin in a concentration-dependent manner. Inhibition by adrenomedullin of FCS- and PDGF-induced SMC migration was paralleled by an increase in the cellular level of cAMP. In fact, the percent increase in cAMP level was strongly correlated with the percent decrease in migration activity of SMCs after treatment with adrenomedullin. 8-Bromo cAMP, a cAMP analogue, reproduced the inhibition by adrenomedullin of FCS- and PDGF-induced SMC migration. An activator of adenylate cyclase, forskolin, also reduced FCS- and PDGF-induced SMC migration. These data indicate that adrenomedullin inhibits the migration of SMCs stimulated with FCS and PDGF, probably through a cAMP-dependent process. On the basis of these results and the finding that adrenomedullin is synthesized in and secreted from vascular endothelial cells, adrenomedullin may play a role as a local antimigration factor in some pathophysiological states.

The present study was designed to test two hypotheses: (1) that angiotensin II (Ang II) stimulates endothelin-1 secretion in cultured rat mesangial cells and (2) that atrial and brain natriuretic peptides (ANP and BNP) inhibit the above-mentioned secretion in these cells. Ang II stimulated immunoreactive (ir) endothelin-1 secretion in a concentration-dependent manner between 10(-8) M and 10(-7) M. The protein kinase C (PKC) inhibitors from two chemical classes, H7 and staurosporine, inhibited secretion following such stimulation. The stimulatory effect of Ang II was also abolished in the PKC-depleted cells. Rat ANP(1-28) and rat BNP-45, which are the respective major circulating forms of ANP and BNP in rats, potently inhibited Ang II-stimulated endothelin-1 secretion in a concentration-dependent manner. Inhibition by ANP and BNP of Ang II-stimulated endothelin-1 secretion was paralleled by an increase in the cellular level of cyclic guanosine 5'-monophosphate (GMP). The addition of a cyclic GMP analogue, 8-bromo cyclic GMP, reduced the stimulated endothelin-1 secretion. Rat ANP(5-25) was less effective that rat ANP(1-28) with respect to inhibiting ir-endothelin-1 secretion and increasing cellular cyclic GMP. These findings indicate that Ang II stimulates endothelin-1 secretion in cultured rat mesangial cells by a mechanism probably involving activation of PKC, and that rat ANP and BNP inhibit this stimulated secretion through a cyclic GMP-dependent process.