15-Keto-prostaglandin F2a is the oxidized product of prostaglandin F2a by 15-hydroxyprostaglandin dehydrogenase, which is present in lung, kidney, placenta and other tissues and catalyzes the NAD- or NADP-dependent dehydrogenation of 15-dydroxyl group. 15-Keto-prostaglandin F2a is further metabolized by its delta13-reduction, beta-oxidation and omega oxidation. The ultimate metabolite is 5a,7a-dihydroxy-11-keto-tetranorprosta-1,16-dioic acid, and excreted in urine. Prostaglandin F2a (PGF2) is one of the earliest discovered and most common prostaglandins is actively biosynthesized in various organs of mammals and exhibits a variety of biological activities, including contraction of pulmonary arteries. PGF2 is mainly synthesized directly from PGH2 by PGH2 9,11-endoperoxide reductase. A small amount of PGF2 is also produced from PGE2 by PGE2 9-ketoreductase. A PGF2 epimer has been reported to exhibit various biological activities, and its levels are increased in bronchoalveolar lavage fluid, plasma, and urine in patients with mastocytosis and bronchial asthma. PGF2 is synthesized from PGD2 by PGD2 11-ketoreductase. Prostaglandins are eicosanoids. The eicosanoids consist of the prostaglandins (PGs), thromboxanes (TXs), leukotrienes (LTs), and lipoxins (LXs). The PGs and TXs are collectively identified as prostanoids. Prostaglandins were originally shown to be synthesized in the prostate gland, thromboxanes from platelets (thrombocytes), and leukotrienes from leukocytes, hence the derivation of their names. All mammalian cells except erythrocytes synthesize eicosanoids. These molecules are extremely potent, able to cause profound physiological effects at very dilute concentrations. All eicosanoids function locally at the site of synthesis, through receptor-mediated G-protein linked signalling pathways.