Bovine adrenals contain, in addition to ouabain, a second inhibitor of the sodium pump.
In the search for endogenous cardiac glycosides, two different inhibitors of the sodium pump have been isolated from bovine adrenals. Inhibitor A with a molecular mass of 600 Da and a UV maximum at 250 nm was purified from 16 kg of bovine adrenals. The pure substance (<1 ng) inhibited the sodium pump of human red blood cells with an affinity similar to that of ouabain, yet it cross-reacted with antibodies against the bufadienolide proscillaridin A but not against the cardenolide ouabain. Inhibitor A was slightly more hydrophilic than ouabain on RP-C18 high pressure liquid chromatography. Hence, it showed properties similar to the proscillaridin A immunoreactivity (Sich, B., Kirch, U., Tepel, M., Zideck, W., and Schoner, W. (1996) Hypertension 27, 1073-1078) that increased in humans with systolic blood pressure and pulse pressure. Inhibitor B of the sodium pump with a molecular mass of 584 Da was purified 10(6)-fold from 20 kg of bovine adrenals. It cross-reacted with antibodies against ouabain but not with antibodies against proscillaridin A and inhibited the sodium pump of human and rat red blood cells with the same affinity as ouabain. All other properties, such as the retention time in a C18-reversed phase chromatography, molecular mass determination by electrospray mass spectrometry and fragmentation pattern, and UV and 1H NMR spectroscopic data, were identical to ouabain. Hence, sodium pump inhibitor B from bovine adrenals is the cardenolide ouabain.
Schneider
R
R
Gesellschaft für Biotechnologische Forschung, D-38124 Braunschweig, Germany.
Wray
V
V
Nimtz
M
M
Lehmann
W D
WD
Kirch
U
U
Antolovic
R
R
Schoner
W
W
D000311:Adrenal Glands / Q000378:metabolism*; D000818:Animals; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D006801:Humans; D013058:Mass Spectrometry; D008970:Molecular Weight; D010042:Ouabain / Q000378:metabolism*; D051381:Rats; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors*; D013056:Spectrophotometry, Ultraviolet
D004791:Enzyme Inhibitors; D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase