Chamber Respirometry Concepts

Chamber Respirometry

• Measures how animals exchange gases (oxygen and carbon dioxide)
• Animals are enclosed in a chamber
• Air continuously flows through the chamber, or gases are sealed
• Measures the concentration of gases in the air exchanged
• Pros:
  • Precise: all expired gases measured
  • Accurate
  • Controlled environment
• Cons:
  • Constrained animal behaviour
  • Risk of asphyxiation or hypercapnia
  • May be messy

Metabolism (Chamber) Treadmill

• Used to get certain animals to exercise
• Animals monitored while exercising.

Chamber Respirometry: Closed System

• Measures oxygen consumption in a chamber
• O2 level drops, measured by detecting % O2, concentration drops
• More efficient to measure all the expired gases
• Pros
  • Efficiently monitors all expired gases
  • Quality of air/water provided easier to control
• Cons
  • Risk of asphyxiation, and hypercapnia if levels get too low or high.
  • Accurate with more time scales

Mask Respirometry

• Measures respiration in animals with masks
• Measures the breathing patterns and rates of animals, and how these change between rest and exercise

Energy and Chances in Activity State

• ATP turnover (rate of the creation of ATP) and the rate that fuel (carbohydrates, fats, oxygen) are supplied to the cells aren't always instantaneous
• Example: exercising - the instantaneous spike in ATP turnover can't be seen immediately

Metabolic Efficiency

• Measures the rate of ATP production using different pathways (fast or slow)
• Aerobic metabolism rate is a slow rate of ATP production.

Rate of ATP Production

• Vary based of the pathway
• Phosphocreatine (fast)
• Glycolysis (fast)
• Aerobic metabolism (slow)

Dependence on Oxygen

• Aerobic metabolism: needs oxygen
• Phosphocreatine and Glycolysis do not require oxygen.

Fuel Diversity

• Phosphocreatine and Carbohydrates used as fuel
• Lipids and Amino acids as stored fuel

O2 Consumption and Metabolic Rate

• O2 consumption/CO2 production measured at a respiratory interface for measuring rates of metabolism
• Does not necessarily reflect real-time O2/CO2 production in tissue

Integrating Power and Metabolic Fuel Source

• Inverse relationship between the maximum power (rate of energy production) and the sustainabilit of that energy (ie: the size of the available energy store)

O2 Consumption and Metabolic Rate

• O2 consumption can remain high after returning to a lower activity level. This is because glycogen stores are being replenished and the breakdown products (lactate and creatine) are being metabolized with aerobic metabolism.
• Cori Cycle- use lactate to produce glucose
• Lactate Shuttle conversion pyruvate to acetyl CoA
• Creatine- helps create ATP (rebuilding of phosphocreatine)

Metabolic Rate: Some Definitions

• Basal Metabolic Rate (BMR): Metabolic rate of a homeothermic animal at rest in a thermal neutral zone, typically after not consuming food recently.
• Standard Metabolic Rate (SMR): Similar to BMR but in a poikilothermic animal.
• Resting Metabolic Rate (RMR): Metabolic rate of an animal under defined resting conditions, not necessarily a defined inactive phase

Maximum Aerobic Metabolic Rate (VO2max)

• Maximum sustained oxygen uptake (VO2).

Supramaximal Metabolic Rate

• Burst of physical activity
• The actualized metabolic rate naturally

Field Metabolic Rate

• The actual realized metabolic rate of an animal acting in its natural environment