Effects of modified hemoglobin solutions on the isolated rabbit heart

The effects of modified hemoglobin (Hb) solutions on the coronary vasculature were studied. Hearts were perfused according to Langendorff with constant flow of Tyrode solution. The solutions studied were stroma- free Hb, prepared by lysis of red blood cells in water (SFHb-lys), or prepared by swelling of red blood cells in hypotonic phosphate buffer (SFHb). The increase in coronary vascular resistance at a dose of 200 mg Hb/dl was 68% for SFHb-lys and 13% for SFHb, respectively. Addition of the modified Hb solutions HbNFPLP and polyHbNFPLP produced an increase in coronary resistance of 11% and 8%, respectively. The left ventricular developed pressure (LVDP) (control value 72 +/- 12 mm Hg) increased by 18 and 12 mm Hg, respectively, for a dose of 250 mg Hb/dl. When HbNFPLP was converted to its met-Hb form the increase in LVDP was reduced to 3 mmHg and the increase in perfusion pressure to 6 mm Hg. We conclude that elimination of stromal contamination from Hb solutions can diminish vasoconstrictor effects. The increase in cardiac pressure development and in coronary vascular resistance found for dilute modified Hb solutions is partly due to an improved oxygen transport to the heart.