Bagrov AY, Dmitrieva RI, Fedorova OV, Hunter AP, Kazakov GP,
Shpen VM
Evidence for a bufodienolide Na/K pump inhibitor in human urine
11th Scientific Meeting, American Society of Hypertension
Am J Hypert
(Apr) 9:133A 1996
Membrane fractions were isolated from Fisher 344 rat aorta to yield
one from perivascular nerve terminals containing the 3 isoform of Na/K
ATPase and another from vascular smooth muscle containing the 3 isoform.
Marinobufagenin (MBG) inhibited Na/K ATPase more potently in smooth muscle
fractions (IC50: 10nM vs 500 nM); conversely,ouabain was more potent in the
neuronal membrane fraction (IC50: 1nM vs 100 nM). MBG-like immunoreactivity
was present in normal rat plasma at 0.7 nM, suggesting the possibility of
physiologic role in vascular smooth muscle. Human plasma and urine also
contains MBG-like immunoreactivity, possibly as one of several endogenous
digitalis-like factors. Isolation and chromatographic purification of the
MBG-like immunoreactivity from human urine suggest that >90% of this
activity is due to authentic MBG, identical to the authentic amphibian
compound.
Comment:
The physiological roles of endogenous digitalis-like factors
remain unclear. These studies suggest endogenous synthesis of MBG in
mammals, including man, and suggest differential effect of these factors on
potential target receptors in the vasculature.
Jason G. Umans, M.D., University of Chicago
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11th Scientific Meeting, American Society of Hypertension
H: Special problems :
Endocrine hypertension