Journal of Applied Physiology, Vol 52, Issue 6 1458-1463, Copyright © 1982 by American Physiological Society
Effects of endogenous glucagon on glucose kinetics in shivering dogs
Y. Minaire, J. Forichon and A. Freminet
Intravenous infusion of D-[3-3H]glucose at a constant rate was used to
measure glucose production (rate of appearance, Ra) and utilization (rate
of disappearance, Rd) in normal overnight-fasted dogs exposed to either
neutral (TaN = +25 degrees C) or cold (TaC = -21 degrees C) ambient
temperature. At TaC the metabolic rate was 4.1 times greater than at TaN
and the dogs remained normothermic under both conditions. During control
periods, cold exposure provoked a 2.2 times increase in hepatic Ra while
plasma glucagon remained unaffected. Between two control periods
somatostatin (1 microgram.kg-1.min-1 iv) and insulin (0.5 mU.kg-1.min-1
intraportal) were infused in such a manner that plasma insulin remained
fairly constant at basal levels while glucagon dropped by 51% (TaN) and 66%
(TaC), these percentages being not significantly different. This selective
glucagon deficiency resulted in a 24% (TaN) and 30% (TaC) reduction in
plasma glucose concentration, due to a 23% (TaN) and 25% (TaC) reduction in
glucose production. There was a significant (r = 0.82, P less than 0.01)
correlation between the control Ra and the reduction induced by the
glucagon deficiency. At TaN and TaC, two significant parallel relationships
were found between hepatic Ra and plasma glucagon concentration suggesting
that glucagon has a modulatory effect on more fundamental mechanisms
triggered by the cold-increased metabolic needs.
