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Limit of detection:
80% B/B0: 3.1 pg/ml
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Sensitivity:
50% B/B0: 15 pg/ml
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Prostaglandin D2 (PGD2) is biosynthesized in the brain by a soluble, 26 kD glutathione-independent lipocalin-type PGD2 synthase.1 PGD2 accumulates in the cerebrospinal fluid (CSF), where it induces physiologic sleep in rats and humans.2 PGD2 is also synthesized by mast cells and leukocytes by a cellular, myeloid-type, glutathione-dependent PGD synthase. This PGD2 which is formed in the intracellular and vascular compartments is rapidly metabolized to 11β-PGF2α.3 Thus, urinary measurements of PGD synthesis are most appropriately focused on the measurement of 11β-PGF2α. Measurement of the parent eicosanoid PGD2 is appropriate in the supernatants of cell cultures, where PGD2 levels may reach several ng/ml, and in CSF, where concentrations of several hundred pg/ml have been measured.4 All studies of PGD2 biosynthesis should take into consideration the chemical instability of PGD2 and its rapid degradation in the presence of serum proteins such as albumin.5 PGD2 also readily degrades in both acidic and basic media to give a variety of decomposition products. Similarly, antigenic protein conjugates of PGD2, synthesized for the production of antisera, show considerable amounts of decomposition. Thus, the resulting antibody response is heterogeneous with poor specificity. This makes PGD2 assay systems based on the parent compound unreliable and difficult to interpret. This PGD2-MOX EIA is based on the conversion of PGD2 to a stable MOX derivative. Treatment of the sample with methoxylamine hydrochloride (MOX HCl) converts PGD2 into PGD2-MOX, preventing its further chemical degradation. The antiserum used in the assay was developed using conjugates of this derivative and is very specific for PGD2-MOX. The assay has been validated against stable isotope dilution GC/MS. Measurements using both techniques on identical samples showed a correlation coefficient of 0.97.
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1
Urade, Y., Tanaka, T., Eguchi, N., et al. Structural and functional significance of cysteine residues of glutathione-independent prostaglandin D synthase. J Biol Chem 270 1422-1428 (1995).
2
Satoh, S., Matsumura, H., Nakajima, T., et al. Promotion of sleep by prostaglandin D2 in rats made insomniac by pretreatment with para-chlorophenylalanine. Neurosci Res 21 41-50 (1995).
3
Roberts, L.J., Sweetman, B.J. Metabolic fate of endogenously synthesized prostaglandin D2 in a human female with mastocytosis. Prostaglandins 30 383-400 (1985).
4
Ujihara, M., Urade, Y., Eguchi, N., et al. Prostaglandin D2 formation and characterization of its synthetases in various tissues of adult rats. Arch Biochem Biophys 260 521-531 (1988).
5
Fitzpatrick, F.A., Wynalda, M.A. Albumin-catalyzed metabolism of prostaglandin D2. Identification of products formed in vitro. J Biol Chem 258 11713-11718 (1983).
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