Meeting Abstract
Carbon monoxide (CO) is known for the toxic property of binding tightly to hemoglobin, forming carboxyhemoglobin (COHb), and can prevent oxygen delivery to tissues when COHb values get too high. However, the recent discovery of 1) heme degradation leading to natural CO production in the body, and 2) therapeutic properties from moderate CO exposure has shed new light on the gas. This natural production of CO in the body leads to approximately 0.4 – 1% COHb in non-smoking humans. The most promising therapeutic potential of moderate CO exposure has been attributed reduction in specific conditions (inflammation, apoptosis, cell proliferation) associated with ischemia-reperfusion events. Due to the increased heme protein stores and repetitive ischemia-reperfusion events associated with the dive response in diving animals, we wanted to investigate endogenous CO levels in the breath (ppm CO) and blood (% carboxyhemoglobin – COHb) of four species of cetaceans (Bottlenose dolphins, short-finned pilot whales, killer whales and beluga whales) and two pinniped species (northern elephant seals and Hawaiian monk seals). Our findings show that animals with the most elevated heme protein stores (elephant seals, monk seals and beluga whales) have increased exhaled CO levels (23ppm, 6ppm and 7ppm, respectively) that mimic those seen in human cigarette smokers (> 6 ppm). However, only the elephant seal displayed dramatic elevations in blood CO with values as high as 17.6% COHb (chronic cigarette smoker: 6-15% COHb). These high values are hypothesized to result from elevated erythrocyte turnover in a species with the highest mass-specific mammalian blood volume and hemoglobin concentrations. We suggest that these natural elevations in CO potentially serve to protect the animals against injuries related to consistent ischemia-reperfusion events associated with a lifestyle of breath-holding and the dive-response.
