Enthalpic partitioning of the reduced temperature sensitivity of O2 binding in bovine hemoglobin

Weber, Roy E.; Fago, Angela; Campbell, Kevin L.

doi:10.1016/j.cbpa.2014.06.012

Cited by 17 publications

(10 citation statements)

References 39 publications

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“…Moreover, the enthalpy of oxygenation was similar in high-altitude and low-altitude deer mouse Hb and was largely unaffected by the presence of anionic cofactors. This observation suggests that – as in bovine Hb (Weber et al 2014) – the T-R shift of deer mouse Hb upon oxygenation is considerably endothermic in nature, whereas the endothermic dissociation of ionic cofactors upon oxygenation plays a minor role. This endothermic transition in quaternary structure correlates with a tighter α1β2 sliding subunit interface identified in crystallographic studies of deer mouse recombinant Hb (Inoguchi et al 2013), with additional interactions between αArg92 and βGln39 and between αArg92 and βAsp43, which are both lacking in human HbA.…”

Section: Discussionmentioning

confidence: 85%

“…The temperature effect of deer mouse Hbs, quantified as the enthalpy of oxygenation ΔH (on average −10.5 kJ mol O 2 −1 , Table 1), was significantly lower than that of human HbA (−50.7 kJ mol O 2 −1 ) (Weber et al 2014) and similar to that of bovine Hb, (Coletta et al 1992; Weber et al 2014), a known example of a temperature-insensitive Hb. ΔH values of deer mouse Hbs were also similar to those of ground squirrels (Revsbech et al, 2013) and moles (Signore et al 2012).…”

Section: Discussionmentioning

confidence: 92%

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Bohr effect and temperature sensitivity of hemoglobins from highland and lowland deer mice

Jensen¹,

Storz²,

Fago³

2016

Comparative Biochemistry and Physiology Part A: Molecular &

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An important means of physiological adaptation to environmental hypoxia is an increased oxygen (O2) affinity of the hemoglobin (Hb) that can help secure high O2 saturation of arterial blood. However, the trade-off associated with a high Hb-O2 affinity is that it can compromise O2 unloading in the systemic capillaries. High-altitude deer mice (Peromyscus maniculatus) have evolved an increased Hb-O2 affinity relative to lowland conspecifics, but it is not known whether they have also evolved compensatory mechanisms to facilitate O2 unloading to respiring tissues. Here we investigate the effects of pH (Bohr effect) and temperature on the O2-affinity of high- and low-altitude deer mouse Hb variants, as these properties can potentially facilitate O2 unloading to metabolizing tissues. Our experiments revealed that Bohr factors for the high- and low-altitude Hb variants are very similar in spite of the differences in O2-affinity. The Bohr factors of deer mouse Hbs are also comparable to those of other mammalian Hbs. In contrast, the high- and low-altitude variants of deer mouse Hb exhibited similarly low temperature sensitivities that were independent of red blood cell anionic cofactors, suggesting an appreciable endothermic allosteric transition upon oxygenation. In conclusion, high-altitude deer mice have evolved an adaptive increase in Hb-O2 affinity, but this is not associated with compensatory changes in sensitivity to changes in pH or temperature. Instead, it appears that the elevated Hb-O2 affinity in high-altitude deer mice is compensated by an associated increase in the tissue diffusion capacity of O2 (via increased muscle capillarization), which promotes O2 unloading.

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Section: Discussionmentioning

confidence: 85%

Section: Discussionmentioning

confidence: 92%

Bohr effect and temperature sensitivity of hemoglobins from highland and lowland deer mice

Jensen¹,

Storz²,

Fago³

2016

Comparative Biochemistry and Physiology Part A: Molecular &

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“…Using this method, the r 2 determination coefficients for the fitted curve exceed 0.995 and the standard errors (s.e.m.) are below 3% of the P 50 and n 50 values (Weber et al, 2014).…”

Section: Methodsmentioning

confidence: 82%

O2 binding and CO2 sensitivity in hemoglobins of subterranean African mole rats

Weber

Jarvis

Fago

et al. 2017

Journal of Experimental Biology

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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 haemoglobin (Hb) function that may mitigate the impact of exogenous and endogenous constraints on the uptake and internal transport of O, we measured haematological characteristics, as well as Hb-O binding affinity and sensitivity to pH (Bohr effect), CO, temperature and 2,3-diphosphoglycerate (DPG, the major allosteric modulator of Hb-O affinity in red blood 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 found no consistent patterns in haematocrit (Hct) and blood and red cell DPG and Hb concentrations or in intrinsic Hb-O affinity and its sensitivity to pH and DPG that correlate with burrowing, sociality and soil type. However, the results reveal low specific (pH independent) effects of CO on Hb-O affinity compared with humans that predictably safeguard pulmonary loading under hypoxic and hypercapnic burrow conditions. The O 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.

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“…Hypoxia was induced by aerating the myography chamber with N 2 gas and monitoring the PO2 with an SI130 O2 electrode and SI929 meter (Strathkelvin Instruments, North Lanarkshire, Scotland). Under these experimental conditions, bovine hemoglobin is~10% saturated with O 2 (46). However, for simplicity we have referred to 90% desaturated hemoglobin as deoxyHb throughout this article; it would be expected that 90% desaturated hemoglobin would have significant reductase activity compared with oxyHb.…”

Section: Methodsmentioning

confidence: 99%

Vasoactivity of nitrite in the iliac artery of the toadRhinella marina

Forgan

Sofele

McNeill

et al. 2018

American Journal of Physiology-Regulatory, Integrative and Comp

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Nitrite ([Formula: see text]) causes vasodilation in mammals due to the formation of (nitric oxide) NO by endogenous [Formula: see text] reduction in the vascular wall. In this study, we determined if a similar mechanism operates in amphibians. Dual-wire myography of the iliac artery from Rhinella marina showed that applied [Formula: see text] caused a concentration-dependent vasodilation in normoxia (21% O; EC: 438 µM). Hypoxia (0.63% O) significantly increased the maximal dilation to [Formula: see text] by 5% ( P = 0.0398). The addition of oxyhemoglobin significantly increased the EC ( P = 0.0144; EC: 2,236 µM) but did not affect the maximal vasodilation. In contrast, partially deoxygenated hemoglobin (90% desaturation) did not affect the EC ( P = 0.1189) but significantly ( P = 0.0012) increased the maximal dilation to [Formula: see text] by 11%. The soluble guanylyl cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) completely abolished the response to [Formula: see text] ( P < 0.0001) and of the nitric oxide synthase inhibitors, only N-(1-imino-3-butenyl)-l-ornithine (vinyl-l-NIO; P = 0.0028) significantly reduced the [Formula: see text] vasodilation. The xanthine oxidoreductase inhibitor allopurinol ( P = 0.927), the nitric oxide-scavenger 2-(4-carboxyphenyl)-4,5-dihydro-4,4,5,5-tetramethyl-1H-imidazolyl-1-oxy-3-oxide (C-PTIO; P = 0.478), and disruption of the endothelium ( P = 0.094) did not affect the [Formula: see text] vasodilation. Incubation of iliac arteries with 1 mM [Formula: see text] did not a cause a change in the cGMP concentration (P = 0.407). Plasma [Formula: see text] was found to be 0.86 ± 0.20 µmol/l, while nitrate ([Formula: see text]) was 19.55 ± 2.55 µmol/l. Both cygb and ngb mRNAs were expressed in the iliac artery, and it is possible that these globins facilitate [Formula: see text] reduction in hypoxia. In addition, [Formula: see text] intracellular disproportionation processes could be important in the generation of NO from [Formula: see text].

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Enthalpic partitioning of the reduced temperature sensitivity of O2 binding in bovine hemoglobin

Cited by 17 publications

References 39 publications

Bohr effect and temperature sensitivity of hemoglobins from highland and lowland deer mice

Bohr effect and temperature sensitivity of hemoglobins from highland and lowland deer mice

O2 binding and CO2 sensitivity in hemoglobins of subterranean African mole rats

Vasoactivity of nitrite in the iliac artery of the toadRhinella marina

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