Human adrenomedullin (ADM), a peptide comprising 52 amino acids, is a circulating hormone with vasodilator properties. We have evaluated its release by the heart following ischaemic myocardial damage, as indicated by elevated levels of the cardiospecific protein troponin-T (Tn-T) during cardiopulmonary bypass. ADM (pg/ml) and Tn-T (ng/ml) were measured in coronary sinus blood before and after aortic cross-clamp and in venous blood 6 ;h after surgery in 22 coronary-bypass patients. Based on the pre- and post-clamp Tn-T levels in the coronary sinus, the patients were divided into group I (no change; n = 10) and group II (two times increase; n = 12). Baseline ADM (362.7±106.2 and 303±58.7 pg/ml in groups I and II respectively; means±S.D.) and Tn-T (0.66±0.14 and 0.57±0.13 ng/ml respectively) levels were similar in both groups. In group I, the post-clamp ADM (317.6±80.8 pg/ml) and Tn-T (0.68±0.15 ng/ml) levels did not change significantly. In group II, the post-clamp ADM levels rose significantly above the baseline, mimicking the change in Tn-T (ADM, 541.4±89.4 pg/ml; Tn-T, 1.37±0.31 ng/ml; P = 0.009). After 6 h, the systemic Tn-T levels were similar in both groups (2.09±0.44 and 1.95±0.52 ng/ml in groups I and II respectively). We suggest that: (1) minor degrees of myocardial ischaemic damage result in release of ADM by the heart, and (2) ADM may play a protective role in the myocardium during an ischaemic insult. This suggests a possible therapeutic role for ADM in the management of intra-operative myocardial ischaemia.

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