title: Right-to-left shunt has modest effects on CO2delivery to the gut during digestion, but compromises oxygen delivery.
abstract: By virtue of their cardiovascular anatomy, reptiles and amphibians can shunt blood away from the pulmonary or systemic circuits, but the functional role of this characteristic trait remains unclear. It has been suggested that right-to-left (R-L) shunt (recirculation of systemic blood within the body) fuels the gastric mucosa with acidified and CO2-rich blood to facilitate gastric acid secretion during digestion. However, in addition to elevatingPCO2, R-L shunt also reduces arterial O2levels and would compromise O2delivery during the increased metabolic state of digestion. Conversely, arterialPCO2can also be elevated by lowering ventilation relative to metabolism (i.e. reducing the air convection requirement, ACR). Based on a mathematical analysis of the relative roles of ACR and R-L shunt on O2and CO2levels, we predict that ventilatory modifications are much more effective for gastric CO2supply with only modest effects on O2delivery. Conversely, elevating CO2levels by means of R-L shunt would come at a cost of significant reductions in O2levels. The different effects of altering ACR and R-L shunt on O2and CO2levels are explained by the differences in the effective blood capacitance coefficients.
authors.affiliation: Zoophysiology, Department of Bioscience, Aarhus University, 8000 Aarhus C, Denmark christian.malte@bios.au.dk.
authors.forename: Christian Lind
authors.identifier: 0000-0002-7003-6370
authors.initials: CL
authors.lastname: Malte
authors.affiliation: Zoophysiology, Department of Bioscience, Aarhus University, 8000 Aarhus C, Denmark.
authors.forename: Hans
authors.initials: H
authors.lastname: Malte
authors.affiliation: Zoophysiology, Department of Bioscience, Aarhus University, 8000 Aarhus C, Denmark.
authors.forename: Lærke Rønlev
authors.initials: LR
authors.lastname: Reinholdt
authors.affiliation: Zoophysiology, Department of Bioscience, Aarhus University, 8000 Aarhus C, Denmark.
authors.forename: Anders
authors.initials: A
authors.lastname: Findsen
authors.affiliation: Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697, USA.
authors.forename: James W
authors.initials: JW
authors.lastname: Hicks
authors.affiliation: Zoophysiology, Department of Bioscience, Aarhus University, 8000 Aarhus C, Denmark.
authors.forename: Tobias
authors.initials: T
authors.lastname: Wang
mesh_terms: D000663:Amphibians / Q000033:anatomy & histology / Q000097:blood / Q000502:physiology*; D000818:Animals; D002245:Carbon Dioxide / Q000097:blood / Q000378:metabolism*; D003198:Computer Simulation; D004063:Digestion; D005753:Gastric Mucosa / Q000098:blood supply / Q000502:physiology; D008954:Models, Biological; D010100:Oxygen / Q000097:blood / Q000378:metabolism*; D010101:Oxygen Consumption; D011659:Pulmonary Gas Exchange; D012104:Reptiles / Q000033:anatomy & histology / Q000097:blood / Q000502:physiology*; D012119:Respiration; D013270:Stomach / Q000098:blood supply / Q000502:physiology
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen
keywords: Gas exchange; Heart; Mathematical model; Reptile; Shunting