Contractile effects of diaspirin cross-linked hemoglobin (DCLHb) on isolated porcine blood vessels.

The effects of diaspirin cross-linked hemoglobin (DCLHb) on vascular tone were examined in arterial and venous rings isolated from mesenteric, renal, femoral, and pulmonary blood vessels. Rings were placed in organ baths at optimal passive tension in Krebs' solution (37 degrees C) and aerated with a mixture of 95% O2/5% CO2. Vessels were treated with increasing concentrations of DCLHb or an iso-osmotic serum albumin solution. All artery and vein rings contracted in the presence of DCLHb. With the exception of the pulmonary vein, the magnitude of the tension increase with DCLHb was greater in the arteries than in the veins. Removal of the endothelium by scraping or the addition of a nitric oxide synthase inhibitor blocked the DCLHb-induced contraction in the pulmonary artery and vein. DCLHb also significantly reduced basal cyclic guanosine-3-5'-monophosphate in the pulmonary vein. These studies suggest that the constrictor activity of DCLHb is due primarily to inhibition of basal nitric oxide-induced relaxation of the vascular smooth muscle.