6-Ketoprostaglandin E1 (6-keto PGE1) is a biologically active and stable prostacyclin (PGI2) metabolite and a substrate for Adenylate cyclase type III. 6-keto PGE1 is a potent coronary vasodilator. 6-keto PGE1 could be elevated in plasma of patients with primary thrombocythaemia. 6-keto-PGE1 has approximately four times less potent antiplatelet activity than PGI2 on a molar basis in man. The cardiovascular and plasma renin activity (PRA) changes are less prominent for 6-keto-PGE1 than PGI2. Salt loading slightly increases urinary 6-keto PGE1. 6-keto-PGE1 elicits the same biological effects as PGI2 in human platelets and in rabbit aorta and mesenteric artery, being, however, less potent. 6-keto-PGE1 dose-dependently stimulates adenylate cyclase activity in membranes of human platelets and cultured myocytes from rabbit aorta and mesenteric artery. The extent of stimulation of the enzyme by 6-keto-PGE1 is the same as elicited by PGI2, while the apparent affinity is lower than that of prostacyclin, both in platelets and in vascular smooth muscle cells. At the level of platelet membranes, 6-keto-PGE1 interacts with the binding sites labelled by PGI2. However, in platelets as well as in mesenteric artery myocytes, 6-keto-PGE1 interacts with only one class of sites as demonstrated either by binding or by adenylate cyclase studies, whereas PGI2 in the same conditions recognizes two different classes. (PMID: 3186779, 3075239, 3472253, 3912001, 3881881, 6391491)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.