Endogenous Ouabain Is Not Ouabain

Correspondence concerning the article No endogenous ouabain is detectable in human plasma by ultra-sensitive UPLC-MS/MS. Clin Chim Acta. 2014;431:87-92 by S. Baecher et al.

“…Our finding is in line with a review article published recently by Lewis et al [3] and several other earlier observations [4][5][6]. …”

Na+/K+-ATPase activity is largely unrelated to proliferation of P19 embryonic stem cells

“…The fact that astrocytes reduce extracellular potassium concentrations through the action of Na + /K + -ATPase in the central nervous system [13,26,27] indicates that it is important to elucidate the mechanism of potassium homeostasis regulation in non-excitable cells. Although endogenous cardiac glycosides have not yet been identified, it has been suggested that they interfere with the function of Na + /K + -ATPase and participate in the onset of hypertension [28]. This evidence supports the need to examine the action of cardiac glycosides on stem cells.…”

Letter to the editor: “Why isn't clinical experience with ouabain more widely accepted?”

“…Given these many related, consistent, and widely replicated observations, the burden is on the few groups (1,9,21) that have been unable to purify EO or to induce hypertension with ouabain to explain why not. Contradictory observations can't both be correct, and negative results are not proof that EO is not ouabain.…”

“…The repeatedly verified analytical (HPLC plus mass spectroscopy, nuclear magnetic resonance, and UV) evidence that mammalian (including human) EO is, in fact, "ouabain" (13, 16 -18, 39, 42) is not mentioned, although this contradicts the Lewis et al view (21). The latter had already been refuted twice (23,24).…”

“…Departments of Physiology and Medicine, University of Maryland School of Medicine, Baltimore, Maryland REPLY: Fürstenwerth (12a) notes that my "Perspectives" on endogenous ouabain (EO) (2) 1) didn't mention the use of ouabain as a therapeutic and antihypertensive agent (true; see last paragraph); 2) didn't consider the view that "(EO) is not 'ouabain'" (21) [I cited an earlier version (32) and the refutation (24); my article (2) Manunta et al (26,27) were, surely, the first to document that cardiotonic steroids (CTS) could antagonize one another and that all CTS do not have identical effects (e.g., ouabain, but not digoxin, causes hypertension). Thus this was "a surprise" in 1993.…”