TY - JOUR
T1 - Changes in hemoglobin function and isoform expression during embryonic development in the American alligator, Alligator mississippiensis
AU - M. Bautista, Naim
AU - Petersen, Elin Ellebæk
AU - Jensen, Rasmus J.
AU - Natarajan, Chandrasekhar
AU - Storz, Jay F.
AU - Crossley, II, Dane A.
AU - Fago, Angela
PY - 2021
Y1 - 2021
N2 - In the developing embryos of egg-laying vertebrates, O
2 flux takes place across a fixed surface area of the eggshell and the chorioallantoic membrane. In the case of crocodilians, the developing embryo may experience a decrease in O
2 flux when the nest becomes hypoxic, which may cause compensatory adjustments in blood O
2 transport. However, whether the switch from embryonic to adult hemoglobin isoforms (isoHbs) plays some role in these adjustments is unknown. Here, we provide a detailed characterization of the developmental switch of isoHb synthesis in the American alligator, Alligator mississippiensis. We examined the in vitro functional properties and subunit composition of purified alligator isoHbs expressed during embryonic developmental stages in normoxia and hypoxia (10% O
2). We found distinct patterns of isoHb expression in alligator embryos at different stages of development, but these patterns were not affected by hypoxia. Specifically, alligator embryos expressed two main isoHbs: HbI, prevalent at early developmental stages, with a high O
2 affinity and high ATP sensitivity, and HbII, prevalent at later stages and identical to the adult protein, with a low O
2 affinity and high CO
2 sensitivity. These results indicate that whole blood O
2 affinity is mainly regulated by ATP in the early embryo and by CO
2 and bicarbonate from the late embryo until adult life, but the developmental regulation of isoHb expression is not affected by hypoxia exposure.
AB - In the developing embryos of egg-laying vertebrates, O
2 flux takes place across a fixed surface area of the eggshell and the chorioallantoic membrane. In the case of crocodilians, the developing embryo may experience a decrease in O
2 flux when the nest becomes hypoxic, which may cause compensatory adjustments in blood O
2 transport. However, whether the switch from embryonic to adult hemoglobin isoforms (isoHbs) plays some role in these adjustments is unknown. Here, we provide a detailed characterization of the developmental switch of isoHb synthesis in the American alligator, Alligator mississippiensis. We examined the in vitro functional properties and subunit composition of purified alligator isoHbs expressed during embryonic developmental stages in normoxia and hypoxia (10% O
2). We found distinct patterns of isoHb expression in alligator embryos at different stages of development, but these patterns were not affected by hypoxia. Specifically, alligator embryos expressed two main isoHbs: HbI, prevalent at early developmental stages, with a high O
2 affinity and high ATP sensitivity, and HbII, prevalent at later stages and identical to the adult protein, with a low O
2 affinity and high CO
2 sensitivity. These results indicate that whole blood O
2 affinity is mainly regulated by ATP in the early embryo and by CO
2 and bicarbonate from the late embryo until adult life, but the developmental regulation of isoHb expression is not affected by hypoxia exposure.
KW - Blood
KW - Hypoxia
KW - Ontogeny
KW - Oxygen transport
KW - Reptile
UR - http://www.scopus.com/inward/record.url?scp=85121008152&partnerID=8YFLogxK
M3 - Journal article
SN - 0363-6119
VL - 321
SP - R869-R878
JO - American Journal of Physiology: Regulatory, Integrative and Comparative Physiology
JF - American Journal of Physiology: Regulatory, Integrative and Comparative Physiology
IS - 6
ER -