Single-injection glucose kinetics with compartmental modelling during rest and low-intensity exercise in horses.
BACKGROUND
Tools and criteria to evaluate and understand glucose metabolism are essential to optimise equine energy utilisation for exercise performance and reduced metabolic health risks.


OBJECTIVE
To re-evaluate models of glucose kinetics in the horse at rest and during endurance type exercise using a single injection technique and compartmental modelling.


METHODS
Twelve exercise trained Arabian geldings received a bolus of 100 µmol/kg bwt [6,6-(2) H]glucose i.v. while at rest and while running at ∼ 4 m/s on a treadmill. Tracer and tracee glucose curves from 4-150 min after the bolus dose (while the subject maintained its resting or exercising state) were described by a 2 term exponential decay curve. Compartmental modelling was performed simultaneously for each horse's resting and exercise curves using an 'exercise effect' parameter for each compartmental exchange rate during exercise.


RESULTS
Exercise increased all rate constants and transport flows for glucose between compartments by 110-145% (P ≤ 0.004). Total glucose transport through the system increased from 8.9 ± 0.6 µmol/min/kg/bwt at rest to 25.0 ± 1.1 µmol/min/kg bwt during exercise (P < 0.001). Exercise decreased the volume of the primary glucose compartment by 8% (P = 0.006) and increased plasma glucose clearance rate by almost 200% (P < 0.001). Turnover times and mean residence times were decreased approximately 60% by exercise (P < 0.001), whilst turnover rates were increased 125% (P < 0.001).


CONCLUSIONS
Single-injection tracer kinetics and compartmental modelling represent a valuable tool to quantify tracee availability to and use by tissue.


CONCLUSIONS
This technique could represent a beneficial tool for future studies exploring the role of glucose metabolism in equine exercise performance and metabolic disease.
Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg, USA. ktreiber@fortworthzoo.org
K H
KH
Treiber
R C
RC
Boston
R J
RJ
Geor
T M
TM
Hess
P A
PA
Harris
D S
DS
Kronfeld
D000818:Animals; D001692:Biological Transport; D001786:Blood Glucose / Q000378:metabolism*; D001835:Body Weight; D005947:Glucose / Q000008:administration & dosage* / Q000493:pharmacokinetics*; D006736:Horses / Q000097:blood / Q000378:metabolism*; D007275:Injections, Intravenous; D008297:Male; D008954:Models, Biological; D010805:Physical Conditioning, Animal / Q000502:physiology*
D001786:Blood Glucose; D005947:Glucose