AJP - Endocrinology and Metabolism, Vol 259, Issue 5 E601-E613, Copyright © 1990 by American Physiological Society
Glucose homeostasis and hypothalamic-pituitary-adrenocortical axis during development in rats
E. P. Widmaier
Department of Biology, Boston University, Massachusetts 02215.
Glucoprivation represents a model stress in which activation of different
stress responses at different ages can be monitored both in vivo and in
vitro. Physiological data indicate rat brain contains a liver/pancreas-type
glucose sensor, yet no biochemical or immunocytochemical evidence exists
for such a sensor. Young rats appear to lack normal hypothalamic
glucose-sensing ability and do not show typical secretory patterns of
corticotropin-releasing factor, adrenocorticotropic hormone, or
corticosterone after experimentally induced glucoprivation. However, they
hypersecrete catecholamines and glucagon (compared with adults) and thrive
on fuel sources other than glucose that are abundant after birth. High
steroid levels during the first 24 h after birth may be critical for
inducing gluconeogenic enzymes and promoting differentiation of tissues
like pancreas. Neonatal rats also have unique control systems to combat the
damaging effects of other stresses like hypoxia; these systems may
disappear in adults. Thus the definition of stress may change during
development, and the compensatory mechanisms employed to combat stress
change from neonatal to adult life and are intricately related to the
metabolic needs of the animal.
