RELEASE OF HISTAMINE FROM ISOLATED RAT HEARTS DURING REPERFUSION IS NOT DEPENDENT ON LENGTH OF ISCHEMIC INSULT, OR CONTENTS OF HISTAMINE INCARDIAC TISSUE

Release of histamine (H) by ischemia-reperfusion injury was investigat ed in isolated rat hearts (Langendorff model). The effect of 10, 15, 2 0, 25, 30, 40 and 60 min ischemia (n = 10 each) on H in the coronary e ffluent and in cardiac tissue was studied after 4 min reperfusion. Rel ease of creatine kinase and lactate dehydrogenase in the coronary effl uent increased with time of ischemia. Tissue H increased from 95 +/- 1 0 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 .0 1), 25 (p < 0.0 1), and 30 min (p < 0.045). H in the coronary efflu ent 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.