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A radioimmunoassay for tetrahydrocortisol
1Department of Medical Neurosciences, Walter Reed Army Institute of Research, Walter Reed Army Medical Center, Washington, D. C. 20012, USA.
Analytical Biochemistry
|December 1, 1978
Summary
A new radioimmunoassay accurately measures urinary tetrahydrocortisol (THF) levels. This method is specific enough for stress experiments, showing high correlation with 17-hydroxycorticosteroids and revealing increased free steroids during stress.
Area of Science:
- Endocrinology
- Biochemistry
- Analytical Chemistry
Background:
- Accurate measurement of urinary tetrahydrocortisol (THF) is crucial for understanding adrenal function.
- Existing methods may lack specificity or require extensive sample preparation.
Purpose of the Study:
- To develop and validate a specific radioimmunoassay (RIA) for quantifying urinary THF.
- To assess the utility of the THF RIA in stress studies without prior purification.
Main Methods:
- Production of antibodies against a THF conjugate.
- Radioimmunoassay procedure involving enzymic hydrolysis, ethyl acetate extraction, and Somogyi reagent separation.
- Analysis of monkey urine during stress experiments.
Main Results:
- The developed antibody demonstrated high specificity for THF, with minimal cross-reactivity.
- Urinary THF levels measured by RIA correlated highly (r=0.97) with 17-hydroxycorticosteroid levels.
- Free unconjugated steroids, including THF, showed the most significant increase during stress.
Conclusions:
- The developed radioimmunoassay provides a specific and reliable method for measuring urinary THF.
- The assay is sufficiently robust for use in stress experiments without requiring sample purification.
- Stress significantly increases free unconjugated cortisol metabolites in urine.