Detection of myoglobin desaturation in Mirounga angustirostris during apnea

1H NMR solution-state study of elephant seal ( Mirounga angustirostris) myoglobin (Mb) and hemoglobin (Hb) establishes the temperature-dependent chemical shifts of the proximal histidyl NδH signal, which reflects the respective intracellular and vascular Po 2 in vivo. Both proteins exist predominantly in one major isoform and do not exhibit any conformational heterogeneity. The Mb and Hb signals are detectable in M. angustirostris tissue in vivo. During eupnea M. angustirostris muscle maintains a well-saturated MbO2. However, during apnea, the deoxymyoglobin proximal histidyl NδH signal becomes visible, reflecting a declining tissue Po 2. The study establishes a firm methodological basis for using NMR to investigate the metabolic responses during sleep apnea of the elephant seal and to secure insights into oxygen regulation in diving mammals.