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O2 binding and CO2 sensitivity in hemoglobins of subterranean African mole rats
Weber, Roy E.; Jarvis, Jennifer U.M.; Fago, Angela; Bennett, Nigel Charles
Inhabiting deep and sealed subterranean burrows, mole rats exhibit a remarkable suite of
specializations, including eusociality (living in colonies with single breeding queens), extraordinary
longevity, cancer immunity and poikilothermy, and extreme tolerance of hypoxia and
hypercapnia.With little information available on adjustments in hemoglobin (Hb) function that may
mitigate the impact of exogenous and endogenous constraints on the uptake and internal transport of
O2, we measured hematological characteristics, as well as Hb-O2 binding affinities and their
sensitivities to pH (Bohr effect), CO2, temperature and 2,3 diphosphoglycerate (DPG, the major
allosteric modulator of Hb-O2 affinity in the red cells) in four social and two solitary species of
African mole rats (family Bathyergidae) originating from different biomes and soil types across
Central and Southern Africa. We find no consistent patterns in hematocrit (Hct) and blood and red cell
DPG and Hb concentrations or in intrinsic Hb-O2 affinity and its sensitivity to pH and DPG that
correlate with burrowing, sociality and soil-type. However, the results reveal low specific (pHindependent)
effects of CO2 on Hb-O2 affinity compared to humans that predictably safeguard
pulmonary loading under hypoxic and hypercapnic burrow conditions. The O2-binding characteristics
are discussed in relation to available information on the primary structure of Hbs from adult and
developmental stages of mammals subjected to hypoxia and hypercapnia and the molecular mechanisms underlying functional variation in rodent Hbs.