Platelet prostaglandin D2 dehydrogenase in patients with myeloproliferative disorders

NADP-linked 15-hydroxyprostaglandin dehydrogenase for prostaglandin D2 (PGD2DH) transforms prostaglandin D2 (PGD2) to inactive 15-keto-PGD2. This enzyme activity was spectrophotometrically determined in the cytosol of platelets and platelet sensitivities to PGD2 were studied in patients with myeloproliferative disorders (MPD) as well as in normal subjects. Platelet sensitivities to exogenous and endogenous PGD2 were estimated by IC50 of added PGD2 for platelet aggregation and by the inhibitory effect of a specific thromboxane synthetase inhibitor (OKY-046) on collagen-induced aggregation, respectively. PGD2DH activities of MPD patients were significantly higher than those of normal subjects (p less than 0.01). Although decreased sensitivity to exogenous PGD2 was detected in some MPD patients, they were not always associated with the increased enzyme activities. Furthermore, no specific correlation was found between PGD2DH activities and the inhibitory effects of OKY-046. Thus, PGD2DH seems to have little effect on the action of PGD2 against platelet aggregation in MPD patients and normal subjects.