| Kinase Assay: |
| J Hypertens. 2002 Jun;20(6):1189-94. | | Marinobufagenin, an endogenous ligand of alpha-1 sodium pump, is a marker of congestive heart failure severity.[Pubmed: 12023690] | A reduced cardiac output in chronic heart failure (CHF) evokes renal NaCl and water retention, and, therefore, activates mechanisms promoting natriuresis. Atrial natriuretic peptide (ANP) is one such factor. We hypothesized that another NaCl sensitive endogenous natriuretic factor, i.e., Marinobufagenin (MBG), a specific ligand of the alpha-1 subunit of Na/K ATPase (the main kidney isoform) and also a vasoconstrictor and cardiotonic substance, would be elevated in CHF patients in a graded manner with the severity of CHF.
METHODS AND RESULTS:
We measured the plasma levels of MBG, alpha-hANP, ouabain-like compound (OLC) and left ventricular (LV) volumes and ejection fraction in 23 consecutive hypertensive male patients with CHF. Plasma MBG levels exhibited progressive increases (0.59 +/- 0.15, 1.08 +/- 0.20, 1.35 +/- 0.17 and 1.88 +/- 0.05 nmol/l NYHA 1-4, respectively) and paralleled the changes of alpha-hANP. Conversely, plasma OLC did not exhibit such increases. Plasma MBG correlated with alpha-hANP (r = 0.82; P < 0.0001). Both MBG and alpha-hANP correlated with LV systolic (r = 0.55 and r = 0.47; P < 0.01) diameter and inversely with ejection fraction (r = -0.73 and r = -0.60; P < 0.01). OLC did not exhibit correlations with alpha-hANP or LV volumes, but positively correlated with systolic brachial blood pressure and with pulse pressure.
CONCLUSIONS:
In CHF, MBG exhibits progressive increases similar to ANP, varies with CHF severity and correlates with LV systolic function. We hypothesize, that, in CHF, the concurrent production of these two natriuretic hormones, a vasorelaxant, ANP, and a vasoconstrictor, MBG, potentiate each other's natriuretic effects, but may offset their vasoactive actions. |
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| Cell Research: |
| Circulation. 2003 Dec 16;108(24):3048-53. | | Ouabain- and marinobufagenin-induced proliferation of human umbilical vein smooth muscle cells and a rat vascular smooth muscle cell line, A7r5.[Pubmed: 14638550] | We studied the growth-promoting effects of 2 sodium pump-selective cardiotonic steroids, ouabain and Marinobufagenin, on cultured cells from vascular smooth muscle (VSMCs) from human umbilical vein and a rat VSMC line, A7r5.
METHODS AND RESULTS:
Both ouabain and Marinobufagenin activated proliferation of these cells in a concentration-dependent manner, reflecting the cardiotonic steroid sensitivity of the specific alpha1 subunit contained within each cell source. The observed effective concentration ranges of both compounds was below that necessary to induce cytoplasmic ion alterations by sodium pump inhibition.
CONCLUSIONS:
These data indicate that the ouabain-activated proliferative effect previously observed in canine VSMCs occurs in other VSMC sources. This growth effect seems to be initiated by drug interaction with the sodium pump, reflected by the affinity of the steroid for the pump, and is independent of altered transmembrane ionic gradients. |
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