The Radioimmunological Estimation of 13,14-Dihydro-15-Ketoprostaglandin E₂ in Plasma and Cervical Mucus

Summary

Highly specific antibodies to 13,14-dihydro-15-ketoprostaglandin E₂ (PGEM) were raised in rabbits. The animals were immunized with PGEM-bovine serum albumin (BSA)-conjugates. The metabolites were extracted with dichloromethane followed by column chromatography.

The final antisera dilution was 1: 15000 and the crossreactivity towards prostaglandin A₂, F_2α, I₂, 13, 14-dihydro-15-ketoprostaglandin F_2α was < 0.1%. The limit of detection was 7.8 ± 4.7 pg/ml plasma at the standard range of 3.9 to 500 pg/ml. The intra- and inter-assay variations were 5 and 12%, respectively. PGEM was measured throughout the menstrual cycle in female volunteers. In normal ovulatory women (n=6) plasma concentrations of PGEM varied between 0.94 to 2.19 ng/ml. A significant increase of plasma PGEM was detected in the preovulatory phase of the cycle (P < 0.01) over basal levels. In three of these volunteers cervical mucus was analyzed on PGEM and PGFM concentrations showing a fluctuation from 2 pg to 109 pg for PGEM and 0.05 pg to 2.4 pg for PGFM per ml of cervical mucus. The lowest concentrations have been found at the time of ovulation. The application of the radioimmunological method to the measurement of PGEM in addition to the measurement of prostaglandin E₂ may be useful for estimating the turnover rates of this fatty acid.

Key-Words:

Radioimmunoassay - 13,14-dihydro-15-ketoprostaglandin E₂ - Menstrual Cycle - Cervical Mucus