Interactions of acid-base balance and hematocrit regulation during environmental respiratory gas challenges in developing chicken embryos (Gallus gallus).
How the determinants of hematocrit (Hct) - alterations in mean corpuscular volume (MCV) and/or red blood cell concentration ([RBC]) - are influenced by acid-base balance adjustments across development in the chicken embryo is poorly understood. We hypothesized, based on oxygen transport needs of the embryos, that Hct will increase during 1 day of hypercapnic hypoxia (5%CO(2), 15%O(2)) or hypoxia alone (0%CO(2), 15%O(2)), but decrease in response to hyperoxia (0%CO(2), 40%O(2)). Further, age-related differences in acid-base disturbances and Hct regulation may arise, because the O(2) transport and hematological regulatory systems are still developing in embryonic chickens. Our studies showed that during 1 day of hypoxia (with or without hypercapnia) Hct increased through both increased MCV and [RBC] in day 15 (d15) embryo, but only through increased MCV in d17 embryo and therefore enhancement of O(2) transport was age-dependent. Hypercapnia alone caused a ≈ 14% decrease in Hct through decreased [RBC] and therefore did not compensate for decreased blood oxygen affinity resulting from the Bohr shift. The 11% (d15) and 14% (d17) decrease in Hct during hyperoxia in advanced embryos was because of an 8% and 9% decrease, respectively, in [RBC], coupled with an associated 3% and 5% decrease in MCV. Younger, d13 embryos were able to metabolically compensate for respiratory acidosis induced by hypercapnic hypoxia, and so were more tolerant of disturbances in acid-base status induced via alterations in environmental respiratory gas composition than their more advanced counterparts. This counter-intuitive increased tolerance likely results from the relatively low [Formula: see text] and immature physiological functions of younger embryos.
Developmental and Integrative Biology, Department of Biological Sciences, University of North Texas, 1155 Union Circle #305220, Denton, TX 76203, USA. burggren@unt.edu
Warren W
WW
Burggren
Sarah J
SJ
Andrewartha
Hiroshi
H
Tazawa
D000136:Acid-Base Equilibrium / Q000502:physiology*; D000693:Anaerobiosis; D000818:Animals; D002245:Carbon Dioxide / Q000502:physiology*; D002642:Chick Embryo; D047108:Embryonic Development; D004909:Erythrocyte Indices / Q000502:physiology; D004912:Erythrocytes / Q000502:physiology*; D006400:Hematocrit; D010100:Oxygen / Q000502:physiology*; D012119:Respiration
D002245:Carbon Dioxide; D010100:Oxygen