Release of histamine from isolated rat hearts during reperfusion is not dependent on length of ischemic insult, or contents of histamine in cardiac tissue.

Release of histamine (H) by ischemia-reperfusion injury was investigated in isolated rat hearts (Langendorff model). The effect of 10, 15, 20, 25, 30, 40 and 60 min ischemia (n = 10 each) on H in the coronary effluent and in cardiac tissue was studied after 4 min reperfusion. Release of creatine kinase and lactate dehydrogenase in the coronary effluent increased with time of ischemia. Tissue H increased from 95 +/- 10 ng/g rat heart (mean +/- SEM) before ischemia to max 148 +/- 10 ng/g after 20 min ischemia (p < 0.002), and increased also after 15 (p < 0.01), 25 (p < 0.01), and 30 min (p < 0.045). H in the coronary effluent increased after 15 (from 16 +/- 3 to 26 +/- 2 pmol/min, p < 0.044), 30 (26 +/- 6 pmol/min, p < 0.027), and 60 min ischemia (47 +/- 6 pmol/min, p < 0.0044). Release of H during ischemia-reperfusion is neither dependent on the severity of the ischemic insult, nor on the level of tissue H.