Simple radioimmunological method for urinary 6-keto-PGF1 alpha measurement

Area of Science:

• Biochemistry
• Analytical Chemistry
• Endocrinology

Background:

• Prostacyclin is a vital vasodilator and inhibitor of platelet aggregation.
• 6-keto-PGF1α is the stable metabolite of prostacyclin, reflecting its activity.
• Accurate measurement of 6-keto-PGF1α in urine is crucial for understanding prostacyclin's physiological and pathological roles.

Purpose of the Study:

• To develop and validate a specific radioimmunoassay (RIA) for quantifying 6-keto-PGF1α in human and animal urine.
• To assess the assay's performance characteristics, including specificity, sensitivity, and precision.
• To measure urinary 6-keto-PGF1α levels in normal and salt-loaded rats, and in healthy adult men and women.

Main Methods:

• A specific antiserum was used for the radioimmunoassay.
• (3H)-6-keto-PGF1α served as the tracer.
• Hydroxyapatite was used for separating bound and free fractions.
• Urine samples underwent pre-extraction with hexane and ethyl ether after acidification.

Main Results:

• The assay demonstrated high specificity with no significant cross-reactivity with other prostaglandins.
• The standard curve ranged from 2 to 1000 pg, enabling urine measurements.
• Intra-assay and inter-assay coefficients of variation were 7.7% and 9.8%, respectively.
• Urinary 6-keto-PGF1α levels were significantly higher in salt-loaded rats compared to normal rats (133 ± 32 ng/24h vs 38.3 ± 4.6 ng/24h).
• Healthy men excreted higher levels of 6-keto-PGF1α (508 ± 94 ng/24h) than healthy women (375 ± 136 ng/24h).

Conclusions:

• The developed radioimmunoassay is a reliable method for determining urinary 6-keto-PGF1α.
• The assay allows for the assessment of prostacyclin production in various physiological and pathological conditions.
• Significant differences in urinary 6-keto-PGF1α excretion were observed between sexes and in response to salt loading.