Hemoglobin-based oxygen carrier distribution inside vascular wall and arterial pressure evolution: is there a...

The hemoglobin-based oxygen carriers (HBOC), like dextran-benzene-tetracarboxylate-hemoglobin (Dex-BTC-Hb), which are present at high concentrations in plasma disturb arterial pressure and induce hypertension. To study if the increase of mean arterial pressure (MAP) is due to the presence of cell-free hemoglobin (Hb) inside abdominal aortic wall, we followed on a model of 50% isovolemic exchange transfusion (IET) in anesthetized guinea pigs, the kinetic of Dex-BTC-Hb distribution inside abdominal aortic wall and we investigated the relationship between arterial pressure modifications and modified Hb distribution. The administration of Dex-BTC-Hb induced instantaneously an increase of MAP that reached its maximum (53% of hypertension from baseline) at 17 min after the end of the IET and was maintained maximally up to 30 min. A significantly decrease of MAP (45% of hypertension from baseline) was observed after 60 min and the baseline level was recovered at 180 min. The investigation of tissue at 17 min by confocal microscopy showed the presence of free Hb in or upon endothelial cells (EC) in intima and in vasa vasorum. At 180 min, the free Hb was found in or upon EC and inside all abdominal aortic wall meanwhile MAP recovered its basal value. These results suggest for the first time that Hb in intima seems to induce the hypertension observed upon IET but can not sustain it even if Hb stayed present in intima and in abdominal aortic wall.