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(Hypertension. 2005;46:e13.)
© 2005 American Heart Association, Inc.

Hypertension Electronic Pages

Oabain-Like Compound Changes Rapidly on Physical Exercise in Humans and Dogs

Worthing Hospital, Worthing, United Kingdom

An extract of the first 250 words of the full text is provided, because this article has no abstract.

To the Editor:

The article by Bauer et al¹ attempts to add further credence to the suggestion that ouabain or a ouabain-like compound is secreted in mammals. The results indicate that under conditions of stress, in this case exercise, there is a dramatic increase in the production of immunologically assayed ouabain. In the studied athletes, this increase was up to 36-fold when expressed as endogenous ouabain immunoreactivity and an 18-fold increase when assayed by inhibition of the sodium pump. Cessation of exercise resulted in a fall in the concentration of ouabain-like compounds with a half-life of 3 to 5 minutes, and it is proposed that this is identical to the so-called -decay or rapid phase of ouabain clearance. This seems unlikely given this observed phenomenon follows bolus intravenous injection and is thought to reflect mixing in the intravascular compartment as well as the initial phase of tissue uptake.² Also the half-life of ouabain measured in plasma has been quoted as between 5 and 50 hours. The data presented differ significantly from data provided by Lewis et al, in which a value for the half-life of plasma ouabain was obtained following bolus intravenous administration in humans.³ Under those conditions, the observed half-life of ouabain was at least 60 minutes as measured by high-performance liquid chromatography as well as by biological activity. Lewis et al also suggested that if ouabain is present in plasma it was at a concentration of less than 0.005 nmol/L, different by several orders of magnitude from the . . . [Full Text of this Article]

Wilhelm Schoner

Institute of Biochemistry and Endocrinology, Justus-Liebig University, Giessen, Germany