Birds have strange red blood cells, at least in comparison to mammals. While they both are responsible for transporting oxygen molecules throughout the body, avian red blood cells have mitochondria and a nucleus. Mammalian red blood cells, on the other hand, are missing a nucleus as well as organelles. By eliminating these structures, mammalian red blood cells are able to carry more oxygen molecules and fold more easily to fit within smaller capillaries.
In a new study published in the American Journal of Physiology – Regulatory, Integrative and Comparative Physiology, researchers explored how avian red blood cells produce a gas called hydrogen sulfide (H2S). Their data show that H2S maintains the structural integrity, longevity, and bioenergetics of avian red blood cells. Interestingly, the mitochondria in avian red blood cells were also shown to make cellular energy (ATP) by oxidizing sulfide. In fact, under low oxygen conditions, the production of ATP was reduced.
Z Jin, Q Zhang, E Wondimu, R Verma, M Fu, T Shuang, HM Arif, L Wu, R Wang. H2S-stimulated bioenergetics in chicken erythrocytes and the underlying mechanism. American Journal of Physiology – Regulatory, Integrative and Comparative Physiology. 319(1): R69-R78, 2020. 10.1152/ajpregu.00348.2019