Platelet-activating factor (PAF-acether; 1-O-octadecyl-2-acetyl-sn-glyceryl-3-phosphorylcholine) induced the release of plasminogen activator in rat, both in vivo and in perfused hind legs. The released plasminogen activator was shown by immunologic and functional criteria to be tissue-type plasminogen activator (t-PA). Release of t-PA by PAF-acether could be inhibited by phospholipase inhibitors and by lipoxygenase inhibitors, but not by cyclooxygenase inhibitors. It is suggested that PAF-acether induces the release of t-PA from vascular endothelial cells by the (calcium-dependent) activation of a phospholipase-lipoxygenase pathway. Chemicals/CAS: 3 amino 1 (3 trifluoromethylphenyl) 2 pyrazoline, 66000-40-6; 4 bromophenacyl bromide, 99-73-0; acetylsalicylic acid, 493-53-8, 50-78-2, 53663-74-4, 53664-49-6, 63781-77-1; diethylcarbamazine, 1642-54-2, 1851-24-7, 90-89-1; docebenone, 80809-81-0; edetic acid, 150-43-6, 60-00-4; indometacin, 53-86-1, 74252-25-8, 7681-54-1; mepacrine, 69-05-6, 83-89-6; nordihydroguaiaretic acid, 500-38-9; plasminogen activator, 9039-53-6; thrombocyte activating factor, 64176-80-3, 65154-06-5; tissue plasminogen activator, 105913-11-9; Calcium, 7440-70-2; Cyclooxygenase Inhibitors; Lipoxygenase Inhibitors; Phospholipases, EC 3.1.-; Plasminogen Activators, EC 3.4.21.-; Platelet Activating Factor