Effects of two endogenous Na+,K(+)-ATPase inhibitors, marinobufagenin and ouabain, on isolated rat aorta.
Previously, we reported that the venom of Bufo marinus toad contains a Na+,K(+)-ATPase inhibitor with potent vasoconstrictor activity. In the present study, using thin-layer chromatography in Silicagel 60 F254 + 366, we separated a vasoactive substance from a mixture of steroids from Bufo marinus venom. Based on chromatographic mobility of this substance and typical color reaction after its vizualization with SbCl3, we identified it as a previously described steroid, marinobufagenin. Vasoconstrictor and Na+,K+ pump inhibitory properties of marinobufagenin were studied in isolated rat aortic rings and compared with those of ouabain. Ouabain (10-100 mumol.1-1) produced weak vasoconstriction, which was blocked by 2 mumol.1-1 phentolamine. 10 mumol.1-1 ouabain stimulated, and at higher concentrations inhibited, the Na+,K+ pump. 2 mumol.1-1 phentolamine abolished the activating effect of 10 mumol.1-1 ouabain on the Na+,K+ pump, but did not alter the inhibitory action of higher concentrations of ouabain. By contrast, marunibufagenin elicited rapid and strong vasoconstriction and inhibited ouabain-sensitive 86Rb uptake. Antidigoxin antibody antagonized the vasoconstrictor responses to marinobufagenin, but not to ouabain. 2 mumol.1-1 phentolamine did not alter the constrictor effect of marinobufagenin. In solid-phase digoxin immunoassay, marinobufagenin demonstrated higher digoxin-like immunoreactivity than ouabain.
Bagrov
A Y
AY
Laboratory of Behavioral Sciences, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, USA.
Roukoyatkina
N I
NI
Pinaev
A G
AG
Dmitrieva
R I
RI
Fedorova
O V
OV
D000664:Amphibian Venoms / Q000737:chemistry / Q000494:pharmacology; D000818:Animals; D000911:Antibodies, Monoclonal; D001011:Aorta / Q000187:drug effects / Q000378:metabolism; D002018:Bufanolides / Q000302:isolation & purification / Q000494:pharmacology*; D002024:Bufo marinus; D002855:Chromatography, Thin Layer; D004071:Digitalis Glycosides / Q000494:pharmacology; D004347:Drug Interactions; D005260:Female; D007118:Immunoassay; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D010042:Ouabain / Q000494:pharmacology*; D010646:Phentolamine / Q000494:pharmacology; D051381:Rats; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors* / Q000187:drug effects; D014662:Vasoconstrictor Agents / Q000494:pharmacology*
D000664:Amphibian Venoms; D000911:Antibodies, Monoclonal; D002018:Bufanolides; D004071:Digitalis Glycosides; D014662:Vasoconstrictor Agents; C093896:marinobufagenin; D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase; D010646:Phentolamine