Effect hypoxia on oxygen transport in sheep with different hemoglobin types

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Abstract
In domestic sheep there exist 2 genetically determined types of hemoglobin which have considerably different O2 affinities. It has been suggested that the hemoglobin type of a sheep may influence its tolerance to hypoxia. To examine this suggestion sheep with different hemoglobins were subjected to a hypoxic stress (a 20-min. exposure to 9.3% O2 in N2) and their cardiovascular and respiratory responses measured. The results obtained showed that sheep with the higher O2 affinity hemoglobin (Hb-A) were more resistant to the imposed hypoxia than sheep with lower O2 affinity hemoglobin (Hb-B). The arterial O2 saturation of sheep with Hb-B fell significantly more than that of sheep with Hb-A, and sheep with Hb-B also had a greater respiratory response. The greater tolerance of sheep with Hb-A was, however, most clearly demonstrated by the data which showed although most sheep with Hb-B suffered cardiac crises before the 20-min. exposure period had elapsed, no crises occurred in any sheep with Hb-A.