['The aim of our experiments was to determine the plasma histamine level in the portal venous (VP) blood during acute coronary occlusion and reperfusion.', '27 adult mongrel dogs of either sex were randomized for three groups: sham-operated controls, occlusion group (group O) and reperfusion group (group R).', 'The left circumflex coronary artery (LCx) was proximally occluded and the occlusion was maintained during 6 h (group O), or after a 60-min occlusion the LCx was reperfused (group R). The portal vein was cannulated to take blood samples for hormone measurements.', 'The plasma histamine concentrations were measured with the radioenzymatic method.', 'The VP plasma histamine level was significantly increased 60 min after the LCx occlusion in groups O (99.9 +/- 40.2 vs. 252.9 +/- 100 pg/ml, mean +/- SD) and R (101.2 +/- 55.1 vs. 179.8 +/- 96 pg/ml), and remained high in group O (240.4 +/- 81 pg/ml), while 2 h after LCx reperfusion it had decreased to the basic level. There was no correlation between the hemodynamic parameters and the portal vein plasma histamine levels.'] Does acute myocardial infarction enhance the portal venous histamine level in dogs?