AJP - Regulatory, Integrative and Comparative Physiology, Vol 260, Issue 3 480-R485, Copyright © 1991 by American Physiological Society
Plasma glucagon, glucose, and free fatty acid concentrations and secretion during prolonged hypothermia in rats
R. Hoo-Paris, M. L. Jourdan, C. Moreau-Hansany and L. C. Wang
Department of Zoology, University of Alberta, Edmonton, Canada.
Impairment of metabolic substrate mobilization and utilization may be a
factor limiting survival in hypothermia. Using a newly developed technique
for maintaining stable low body temperature (Tb), substrate profiles and
their regulation by glucagon were examined in hypothermic rats (Tb 19 +/-
0.3 degrees C) over 20 h. During cooling, plasma glucagon, glucose, and
free fatty acid (FFA) concentrations increased significantly (536 +/- 55
pg/ml, 304 +/- 26 mg/100 ml, and 844 +/- 81 mueq/l, respectively). Plasma
glucagon and glucose concentrations continued to increase up to 8 h (peaks
810 +/- 103 pg/ml and 451 +/- 33 mg/100 ml, respectively) and remained high
throughout the rest of the hypothermic period. FFA concentrations decreased
steadily during the hypothermic period. Exogenous glucagon (20
micrograms/kg) induced significant increases in plasma glucose (+129 +/- 31
mg/100 ml) and FFA concentrations (+351 mueq/l) at 2 h but had no effect at
15 h of hypothermia. In vitro evaluation of pancreatic alpha-cell function
indicated that glucagon secretion is independent of temperature between 37
and 19 degrees C. Our data indicate that hypothermia is characterized by a
disturbed substrate metabolism, which is likely due to an imbalance in
pancreatic alpha- and beta-cell function and a time-dependent decrease in
tissue sensitivity to glucagon. These deleterious changes may limit
survival in hypothermia.
