title: Blood oxygen transport in common map turtles during simulated hibernation.
abstract: We assessed the effects of cold and submergence on blood oxygen transport in common map turtles (Graptemys geographica). Winter animals were acclimated for 6-7 wk to one of three conditions at 3 degrees C: air breathing (AB-3 degrees C), normoxic submergence (NS-3 degrees C), and hypoxic (PO2=49 Torr) submergence (HS-3 degrees C). NS-3 degrees C turtles exhibited a respiratory alkalosis (pH 8.07; PCO2=7.9 Torr; [lactate]=2.2 mM) relative to AB-3 degrees C animals (pH 7.89; PCO2=13.4 Torr; [lactate]=1.1 mM). HS-3 degrees C animals experienced a profound metabolic acidosis (pH 7.30; PCO2=7.9 Torr; [lactate]=81 mM). NS-3 degrees C turtles exhibited an increased blood O2 capacity; however, isoelectric focusing revealed no seasonal changes in the isohemoglobin (isoHb) profile. Blood O2 affinity was significantly increased by cold acclimation; half-saturation pressures (P50's) for air-breathing turtles at 3 degrees and 22 degrees C were 6.5 and 18.8 Torr, respectively. P50's for winter animals submerged in normoxic and hypoxic water were 5.2 and 6.5 Torr, respectively. CO2 Bohr slopes (Delta logP50/Delta pH) were -0.15, -0.16, and -0.07 for AB-3 degrees C, NS-3 degrees C, and HS-3 degrees C turtles, respectively; the corresponding value for AB-22 degrees C was -0.37. The O2 equilibrium curve (O2EC) shape was similar for AB-3 degrees C and NS-3 degrees C turtles; Hill plot n coefficients ranged from 1.8 to 2.0. The O2EC shape for HS-3 degrees C turtles was anomalous, exhibiting high O2 affinity below P50 and a right-shifted segment above half-saturation. We suggest that increases in Hb-O2 affinity and O2 capacity enhance extrapulmonary O2 uptake by turtles overwintering in normoxic water. The anomalous O2EC shape and reduced CO2 Bohr effect of HS-3 degrees C turtles may also promote some aerobic metabolism in hypoxic water.
authors.affiliation: Department of Biological Sciences, DePaul University, Chicago, Illinois 60614, USA. lmaginni@depaul.edu
authors.forename: Leigh A
authors.initials: LA
authors.lastname: Maginniss
authors.forename: Summer A
authors.initials: SA
authors.lastname: Ekelund
authors.forename: Gordon R
authors.initials: GR
authors.lastname: Ultsch
mesh_terms: D000064:Acclimatization / Q000502:physiology*; D000136:Acid-Base Equilibrium / Q000502:physiology; D000818:Animals; D003080:Cold Temperature; D006400:Hematocrit; D006454:Hemoglobins / Q000378:metabolism; D007036:Hypothermia, Induced; D007101:Immersion; D007525:Isoelectric Focusing; D010100:Oxygen / Q000097:blood* / Q000378:metabolism; D012621:Seasons; D013053:Spectrophotometry; D013696:Temperature; D014426:Turtles / Q000097:blood* / Q000502:physiology
chemical_list: D006454:Hemoglobins; D010100:Oxygen