Zinc transport by the heart lymphatic system after acute myocardial infarction

Open-chest dog preparations were used to determine divalent cation transport following acute myocardial infarction. Cardiac lymph flow, lymph and plasma protein, zinc, calcium, and magnesium content and hemodynamic measurements were recorded every 20 min before and after coronary artery occlusion in sham operated (N = 4), infarcted (N = 6), and lymph-ablated animals (N = 4). During the 4-hr occlusion period, with constant blood pressure, lymph flow increased from 1.53 +/- 0.25 to 2.15 +/- 0.44 mg/hr (SEM), P less than 0.01. Zinc decreased in plasma from 0.69 +/- 0.10 to 0.41 +/- 0.08 micrograms/ml, P less than 0.01, and in lymph from 0.69 +/- 0.08 to 0.40 +/- 0.02 micrograms/ml, P less than 0.01. Zinc to protein ratio decreased similarly to total zinc in plasma and lymph. Changes in calcium and magnesium were insignificant. Lymph to plasma concentration ratios increased for protein from 0.57 +/- 0.05 to 0.62 +/- 0.02, P less than 0.05, and for zinc from 1.10 +/- 0.26 to 1.21 +/- 0.14, P less than 0.05. Heart lymph clearance (lymph:plasma ratio X lymph flow) steadily rose for protein from 0.31 to 0.06 to 0.50 +/- 0.08, P less than 0.05, and for zinc from 0.59 +/- 0.18 to 0.92 +/- 0.15, P less than 0.05. Lymph and plasma measurements did not change significantly in sham-operated animals. Plasma zinc remained unchanged from baseline after coronary occlusion in all lymph-ablated animals. The increased clearance of protein and zinc suggests that plasma proteins are zinc carriers after acute myocardial infarction and that the reduction of plasma zinc is dependent upon an intact cardiac lymphatic circulation.