Do human platelets express COX-2?

The rate-limiting enzyme in prostaglandin (PG)- and thromboxane (TX)-synthe sis is known as cyclooxygenase (COX). The COX-enzyme family consists of the classical COX-1 and the inducible COX-2-enzyme. To investigate whether pla telets contain COX-2, we measured thiobarbituric acid reactive substances ( TBARS) after either blocking COX-1 or COX-2 or adding compounds known to af fect COX-expression. To stimulate platelets' different reagents such as col lagen, thrombin and arachidonic acid (AA) were used. The inhibitors used in this study were acetylsalicylic acid (ASA), indomethacin and NS-398. Using the western-blot technique, we failed to detect COX-2 in platelets while C OX-1 was detectable. We were not able to discover COX-2 in platelets using the methods we applied. As the amount of COX-2 in platelets might be below the detection limit of the methods used, the biological relevance COX-2 in platelets, if even existing at low amounts, remains to be established. (C) 2001 Harcourt Publishers Ltd.