Blood respiratory properties in the naked mole rat Heterocephalus glaber, a mammal of low body temperature.

Abstract

Respiratory properties of whole blood and Hb solutions have been studied in Heterocephalus glaber, a fossorial rodent, having a low body temperature (30.0-32.0 degrees C) and poor thermoregulatory ability. For comparison similar, measurements were made on laboratory mice, Mus musculus. Whole blood showed a distinctly higher O2 affinity for Heterocephalus at both 30 and 37 degrees C.P50 values were 23.3 mm Hg and 33.0 mm Hg at 37 degrees C for Heterocephalus and Mus, respectively, while at 30 degrees CP50's were 18.8 mm Hg and 24.9 mm Hg, all values at pH (b) 7.4. deltaH values (expressive of the effect of temperature on P50) were -5.8 kcal-mol-1 for Heterocephalus and -7.5 kcal-mol-1 for Mus. The CO2 Bohr effects (omega) were -0.43 and -0.50 for Heterocephalus at 37 and 30 degrees C. Corresponding values for Mus were -0.65 and -0.56. Both species had a Hill's n-value of 2.6. Red cell concentrations of 2,3-DGP were closely similar in the species being 7.3 mmol-L-1 rbc for Heterocephalus and 7.4 mmol-L-1 rbc for Mus. Stripped Heterocephalus Hb had a very high O2 affinity, at pH 7.25, 37 degrees C,P50 was 8.0 mm Hg whereas the corresponding value for Mus was 11.3 mm Hg. Addition of DPG to stripped Hb from the two species decreased O2 affinity to the same degree. The high O2 affinity of Heterocephalus blood is viewed as a possible adaptation to its burrowing habits. Its basis is inherent to the hemoglobin molecule itself and not dependent upon cofactor influence or the temperature sensitivity of the O2-Hb binding.