Right-to-left shunt has modest effects on CO2 delivery to the gut during digestion, but compromises oxygen delivery

@article{Malte2017RighttoleftSH,
  title={Right-to-left shunt has modest effects on CO2 delivery to the gut during digestion, but compromises oxygen delivery},
  author={Christian Lind Malte and Hans Malte and L{\ae}rke R{\o}nlev Reinholdt and Anders Findsen and James W Hicks and Tobias Wang},
  journal={Journal of Experimental Biology},
  year={2017},
  volume={220},
  pages={531 - 536}
}
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 elevating PCO2, R–L shunt also reduces arterial O2… 

Figures and Tables from this paper

Does the left aorta provide proton-rich blood to the gut when crocodilians digest a meal?
TLDR
The findings do not support the hypothesis that a R–L shunt serves to deliver CO2 for the gastrointestinal system after feeding in crocodilians, and blood in the left aorta of American alligators does not contain elevated PCO2 levels during digestion.
Ectothermy and cardiac shunts profoundly slow the equilibration of inhaled anaesthetics in a multi-compartment model
TLDR
A new computational model predicting equilibration of inhaled anaesthetics in mammalian and ectotherm conditions including the ability of reptiles to maintain vascular shunts is developed and clinical strategies to regulate anaesthetic uptake in ectotherms are explored.
Cardiovascular shunting in vertebrates: a practical integration of competing hypotheses
TLDR
It is argued that deposing the ‘monolithic’ view of shunting leads to a more nuanced view of vertebrate cardiovascular systems, and suggests new paradigms for testing the function of shunts.
Feeding alters blood flow patterns in the American alligator (Alligator mississippiensis).
New insights into the allosteric effects of CO2 and bicarbonate on crocodilian hemoglobin.
Crocodilians are unique among vertebrates in that their hemoglobin (Hb) O2 binding is allosterically regulated by bicarbonate, which forms in the red blood cell upon hydration of CO2. Although known

References

SHOWING 1-10 OF 29 REFERENCES
The interaction of pulmonary ventilation and the right-left shunt on arterial oxygen levels.
TLDR
It is proposed that, in future experiments, the measurement of both ventilatory and cardiovascular parameters must be combined if the authors aim to understand the regulation of arterial blood gas levels in lower vertebrates.
Ligation of the left aorta in alligators affects acid–base balance: A role for the R→L shunt
Patterns of cardiovascular and ventilatory response to elevated metabolic states in the lizard Varanus exanthematicus.
TLDR
The results indicate that, in these lizards, the cardiac response to elevated vdot (O2) is stereotyped, the response being predictable irrespective of the source of the metabolic increment.
Susceptibility of different gases to ventilation-perfusion inequality.
  • P. Wagner
  • Engineering
    Journal of applied physiology: respiratory, environmental and exercise physiology
  • 1979
TLDR
An algebraic analysis of inert gas exchange in two-compartment models of both series and parallel inequality is presented and account for the observation that CO2 transfer is compromised in many examples of series inequality.
Effects of feeding on arterial blood gases in the American alligator Alligator mississippiensis.
TLDR
The view that the specific HCO3(-) effect prevents an increased blood oxygen-affinity during digestion in alligators is supported, as the in vitro blood oxygen -affinity was reduced during the post-prandial period, whereas the estimated in vivo blood oxygen,affinity remained virtually constant.
Surgical removal of right-to-left cardiac shunt in the American alligator (Alligator mississippiensis) causes ventricular enlargement but does not alter apnoea or metabolism during diving
TLDR
While surgical removal of R–L shunt in American alligators causes considerable changes in cardiac morphology similar to aortic banding in mammals, its removal does not affect the respiratory pattern or metabolism of alligators, and it appears probable that the low metabolic rate of reptiles allows for normal aerobic dives.
The Right‐to‐Left Shunt of Crocodilians Serves Digestion
TLDR
It is hypothesized that the foramen of Panizza functions to enrich with oxygen blood that is destined for the gastrointestinal system to power proton pumps and other energy‐demanding processes of digestion and that the right‐to‐left shunt serves to provide carbon dioxide to gastrointestinal organs besides the stomach, such as the pancreas, spleen, upper small intestine, and liver.
Pulmonary gas exchange during intermittent ventilation in the American alligator.
The respiratory consequences of feeding in amphibians and reptiles.
Ventilatory and cardiovascular responses of a python (Python molurus) to exercise and digestion.
TLDR
The capacities of the ventilatory and cardiovascular systems to transport oxygen to locomotor muscles are not a limiting factor in the attainment of peak metabolic rates during exercise in pythons.
...
1
2
3
...