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Glucose infusion into exercising dogs after confinement: rectal and active muscle temperatures
J E Greenleaf1, B Kruk, K Nazar
1Laboratory for Human Environmental Physiology, NASA-Ames Research Center, Moffett Field, CA 94035-1000, USA.
Background:
Intravenous glucose infusion into ambulatory dogs results in attenuation of exercise-induced increase of both rectal and thigh muscle temperatures.
Hypothesis:
That glucose (Glu) infusion attenuates excessive increase in body temperature from restricted activity during confinement deconditioning.
Methods:
Rectal (Tre) and quadriceps femoris muscle (Tmu) temperatures, metabolic rate, and blood samples were taken before and after 90 min of moderate treadmill exercise (mean = 3.1 +/- SE 0.2 W.kg-1) at Tdb = 21 +/- 1 degrees C and 45-60% rh from 7 male mongrel dogs (19.6 +/- SD 3.0 kg) with i.v. infusion of 40% Glu in 0.9% NaCl (0.07 ml.kg-1.min-1) or 0.9% NaCl (0.07 mg.g-1.min-1) both before and after 8 weeks of cage confinement.
Results:
Mean (+/- SE) delta Tre (90-0 min) were: NaCl.after = 1.8 +/- 0.4 degrees C vs. 1.4 +/- 0.3 degrees C (NS) before confinement; Glu.after = 1.3 +/- 0.2 degrees C vs. 0.9 +/- 0.3 degrees C (p < 0.02) before confinement. Comparable delta Tmu (90-0 min) data were: NaCl.after = 2.5 +/- 0.4 degrees C vs. 1.9 +/- 0.4 degrees C (NS) before; Glu.after = 1.6 +/- 0.2 degrees C vs. 1.4 +/- 0.4 degrees C (NS) before. Glucose infusion significantly attenuated the rise of Tmu (1.9 degrees vs. 1.4 degrees C) only before confinement, but attenuated the rise of Tre both before (1.4 degrees vs. 0.9 degrees C) and after (1.8 degrees vs. 1.3 degrees C) confinement. Body temperature attenuation was not related to change in plasma volume, osmolality, [Glu], [lactate], [cortisol], or heat production with constant VO2.
Conclusion:
Intravenous glucose infusion attenuates the rise in exercise core temperature in deconditioned dogs by a yet undefined mechanism.