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Clinical Chemistry, Vol 42, 1949-1954, Copyright © 1996 by American Association for Clinical Chemistry
YK Semra, AN Butt and R Swaminathan
Department of Chemical Pathology, UMDS, Guy's & St Thomas' Hospital, London.
Recent studies suggest that ouabain or a ouabain-like substance (OLS) may be present endogenously in humans. We developed a RIA for ouabain with antisera raised in goat against ouabain conjugated to keyhole limpet hemocyanin and ovalbumin. The antiserum was of high antibody titer (200,000) and was specific for ouabain, with little cross- reactivity with common steroids and structurally related compounds such as ouabagenin (4%), strophanthidin (4%), and dihydroouabain (2%). The RIA had a working range of 0.06-2.0 nmol/L, and the intra- and interassay CV was 6.5% at a concentration of 1.7 nmol/L. With this assay the effect of salt loading on urinary excretion of OLS was examined in 10 healthy volunteers (ages 18-22 years) who increased their salt intake (sodium) for 5 days and reduced it for the next 5 days. Urine was collected and OLS concentration was measured by RIA after solid-phase extraction with a Bond Elut C18 column. Excretion of OLS and sodium were maximal on day 5 and lowest on days 9 and 10. Urine excretion of OLS on day 5 (2.66 +/- 1.22 nmol/24 h) was significantly higher (P < 0.0001) than on day 10 (1.47 +/- 0.69 nmol/24 h). We conclude that (a) the assay developed has sufficient sensitivity and specificity to detect endogenous OLS present in biological fluids, and (b) salt intake increases the excretion of OLS.
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O. Vakkuri, S. S. Arnason, P. Joensuu, J. Jalonen, O. Vuolteenaho, and J. Leppaluoto Radioiodinated Tyrosyl-Ouabain and Measurement of a Circulating Ouabain-like Compound Clin. Chem., January 1, 2001; 47(1): 95 - 101. [Abstract] [Full Text] [PDF] |
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C. S. Ho, A. Butt, Y. K. Semra, and R. Swaminathan Effect of Carbidopa on the Excretion of Sodium, Dopamine, and Ouabain-Like Substance in the Rat Hypertension, December 1, 1997; 30(6): 1544 - 1548. [Abstract] [Full Text] |
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