title: Dynamics of acid-base metabolic compensation and hematological regulation interactions in response to CO2 challenges in embryos of the chicken (Gallus gallus).
abstract: CO2 exposure elicits multiple changes in the acid-base balance and hematology of avian embryos, but the time-specific, dose-dependent effects of graded increases in extrinsic CO2 in a normoxic environment are poorly understood. Consequently, we exposed day 15 chicken embryos to 1, 3, 5, 6 or 10% CO2 in 20% O2. We hypothesized that both the magnitude of hypercapnic respiratory acidosis and the resultant metabolic compensation within 24 h of exposure to <10% CO2 are proportional to ambient CO2 concentration ([CO2]). We also predicted that regulation of hematological respiratory variables is graded according to [CO2]. Time-course (2, 6 and 24 h) changes were determined for acid-base disturbances and hematological respiratory variables; hematocrit (Hct), red blood cell concentration ([RBC]), hemoglobin concentration, mean corpuscular volume (MCV) and other mean corpuscular indices. Both the decrease in uncompensated pH, which indicates uncompensated respiratory acidosis, and the compensatory pH increase, a sign of metabolic compensation, increased with [CO2]. The partial metabolic compensation across all CO2 gas mixtures was ~17, 46 and 53% compensation at 2, 6 and 24 h, respectively. Hematological responses were nearly identical across the entire range of [CO2], with Hct decreasing across the time course of CO2 exposure due to a decrease in MCV from 2 to 24 h and a decrease in [RBC] at 24 h. Even though hematological regulation was not graded, chicken embryos were able to compensate and survive exposure to <10% CO2.
authors.affiliation: Developmental Integrative Biology, Department of Biological Sciences, University of North Texas, 1155 Union Circle #305220, Denton, TX, 76203, USA, caseyamueller@gmail.com.
authors.forename: Casey
authors.initials: C
authors.lastname: Mueller
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Tazawa
authors.forename: Warren
authors.initials: W
authors.lastname: Burggren
mesh_terms: D000136:Acid-Base Equilibrium / Q000187:drug effects*; D000142:Acidosis, Respiratory / Q000139:chemically induced; D000818:Animals; D002245:Carbon Dioxide / Q000494:pharmacology*; D002642:Chick Embryo; D004906:Erythrocyte Count; D004909:Erythrocyte Indices; D006400:Hematocrit; D006454:Hemoglobins / Q000032:analysis; D006935:Hypercapnia / Q000378:metabolism
chemical_list: D006454:Hemoglobins; D002245:Carbon Dioxide