Characterization of ouabain-like immunoreactivity in human urine


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Abstract

ObjectiveTo characterize ouabain-like immunoreactivity in human urineMethodsSensitive radioimmunoassay for ouabain characterized by high- performance liquid chromatographyResultsSerial dilution of urinary immunoreactive ouabain paralleled the standard curve, but not so plasma immunoreactive ouabain. Intravenous administration of 86nmol (62.5 μg) ouabain caused a rapid rise in ouabain immunoreactivity in plasma of healthy volunteers with a maximum of 1.7nmol/l 8min after injection and returned to basal levels after 6 h. Ouabain immunoreactivity rose to 36 nmol/l in urine, suggesting that exogenously administered ouabain can be measured reliably in plasma and urine. Analytical reversed-phase high-performance liquid chromatography (isopropanol-propanol biphasic gradient; linear acetonitrile gradient) of sample extracts before assay demonstrated measurable amounts of ouabain-related material only in native urine, but not in plasma. When plasma and urine were spiked with ouabain standard or normal volunteers were injected with ouabain, the assay reliably measured ouabainConclusion:A substance closely related to ouabain can be detected in urine, but circulates, if at all, in small amounts in human plasma

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