Effects of diaspirin crosslinked hemoglobin infusion in treadmill-exercised swine

Confirmation and quantification of hemoglobin-based oxygen carriers in equine and human plasma by hyphenated liquid chromatography tandem mass spectrometry

Oxyglobin (OXY) and Hemopure (HMP) are produced from bovine hemoglobin (Hb) and were developed for the treatment of anemia in animal and human patients, respectively. Hemolink (HML) is a blood substitute of human Hb origin under development. The ability of these agents to carry oxygen in circulating blood and their promise to improve oxygen delivery to tissues supports the potential for their abuse in equine and human athletes. To deter athletes from abuse of these agents, a method has been developed for the detection, confirmation and quantification of OXY, HMP, and HML in equine and human plasma. OXY, HMP, and HML were extracted from equine or human plasma by solid-phase extraction using Bond Elut ENV cartridges and were digested by trypsin at 37 degrees C for 3 h. The tryptic digests were analyzed by LC-MS/MS, and tryptic peptides specific for bovine and human Hbs were targeted. OXY and HMP were detected, quantified, and confirmed using the y14 ion and b8 ion of the tryptic peptide from bovine Hb alpha chain residues 69-90, and HML was quantified using the tryptic peptide from human Hb alpha chain residues 63-91. The limit of detection for OXY in equine plasma and HML in human and equine plasma was 50 and 250 microg/mL for HMP in human and equine plasma. The limit of confirmation was 250 microg/mL for OXY in equine plasma, 500 microg/mL for HML in human and equine plasma, and 1000 microg/mL for HMP in human and equine plasma. The linear range for quantification was 50-5000 microg/mL for OXY in equine plasma and for HML in human and equine plasma, and 250-5000 microg/mL for HMP in human and equine plasma. The intraday and interday CV were less than 17% for quantification of OXY in equine plasma with external calibration. OXY was stable for more than 30 days at -20 and -70 degrees C. OXY was detected and quantified in equine plasma up to 24 h following administration of a very low dose of OXY (32.5 g in 2 x 125 mL per horse), and its presence in equine plasma was confirmed up to 12 h postadministration.

Doping with Artificial Oxygen Carriers

There is a long history of science seeking to develop artificial substitutes for body parts damaged by disease or trauma. While defective teeth and limbs are commonly replaced by imitations without major loss of functionality, the development of a substitute for red blood cells has proved elusive. There is a permanent shortage of donor blood in western societies. Nevertheless, despite whole blood transfusions carrying measurable risks due to immunogenicity and the transmission of blood-borne infectious diseases, red blood cells are still relatively inexpensive, well tolerated and widely available. Researchers seeking to develop products that are able to meet and perhaps exceed these criteria have responded to this difficult challenge by adopting many different approaches. Work has focussed on two classes of substances: modified haemoglobin solutions and perfluorocarbon emulsions. Other approaches include the creation of artificial red cells, where haemoglobin and supporting enzyme systems are encapsulated into liposomes. Haemoglobin is ideally suited to oxygen transport when encased by the red cell membrane; however, once removed, it rapidly dissociates into dimers and is cleared by the kidney. Therefore, it must be stabilised before it can be safely re-infused into humans. Modifications concomitantly alter the vascular half-life, oxygen affinity and hypertensive characteristics of raw haemoglobin, which can be sourced from outdated blood stores, genetically-engineered Escherichia coli or even bovine herds. In contrast, perfluorocarbons are entirely synthetic molecules that are capable of dissolving oxygen but biologically inert. Since they dissolve rather than bind oxygen, their capacity to serve as a blood substitute is determined principally by the oxygen pressure gradients in the lung and at the target tissue. Blood substitutes have important potential areas of clinical application including red cell replacement during surgery, emergency resuscitation of traumatic blood loss, oxygen therapeutic applications in radiography (oxygenation of tumour cells is beneficial to the effect of certain chemotherapeutic agents), other medical applications such as organ preservation, and finally to meet the requirements of patients who cannot receive donor blood because of religious beliefs. Given the elite athlete's historical propensity to experiment with novel doping strategies, it is likely that the burgeoning field of artificial oxygen carriers has already attracted their attention. Scientific data concerning the performance benefits associated with blood substitutes are virtually nonexistent; however, international sporting federations have been commendably proactive in adding this category to their banned substance lists. The current situation is vulnerable to exploitation by immoral athletes since there is still no accepted methodology to test for the presence of artificial oxygen carriers.

Haemoglobin-based erythrocyte transfusion substitutes

Concerns about the infectious and immunosuppressive risks of allogeneic blood products persist, and the increased disproportion of blood donation and consumption has reinforced the search for alternative erythrocyte transfusion strategies in recent years. With the absence of problems such as nephro-toxicity, increased colloid osmotic pressure and sudden renal clearance, modern haemoglobin based oxygen carriers (HBOC) have shown their effectiveness and tolerability in numerous animal and several clinical studies. HBOC can be infused without prior cross-matching and are now available as stable formulations with long shelf-life. Most clinical studies have been performed with human cross-linked haemoglobin (DCLHb) but all trials were stopped two years ago because of an increased mortality in two clinical trials in patients who received DCLHb after stroke and multiple injury shock. However, experimental trials in animals are in progress with DCLHb and recombinant human haemoglobin. In contrast, Phase III studies with polymerised bovine haemoglobin (HBOC-201) are finished or currently under evaluation showing that infusion of HBOC-201 can avoid or reduce allogeneic blood transfusion needs in specific peri-operative settings. As a consequence, HBOC-2001 was actually approved for treatment of peri-operative anaemia in elective adult surgical patients in South Africa. Other human or bovine haemoglobin solutions are currently being investigated in different clinical studies in cardiac surgery patients, sepsis and tumour patients. More recent investigations have shown that HBOC are not only simple erythrocyte transfusion substitutes but highly effective oxygen donators in terms of tissue oxygenation. HBOC open the door for a new therapeutic strategy: plasmatic oxygen delivery with physiological concentrations of inspired oxygen. In specific situations (e.g., ischaemia or arterial stenosis) HBOC have advantages over red blood cells because they can reach post-stenotic or poorly perfused tissues with the plasma stream, where erythrocytes are not able to pass. In addition to significant plasmatic oxygen transport, HBOC also enhance tissue oxygenation because of the facilitated oxygen release by HBOC and from remaining erythrocytes. Further studies will show, if the outcome of patients with impaired perfusion (e.g., stroke or myocardial infarction) can be improved by prophylactic or therapeutic application of HBOC. Whenever these formulations are globally launched, they will find differential indications as potent oxygen-delivering drugs in addition to the globally recognised goal of red cell substitutes in cases of bleeding.