Journal of Applied Physiology, Vol 50, Issue 2 367-373, Copyright © 1981 by American Physiological Society
Age and altitude tolerance in rats: temperature, plasma enzymes, and corticosterone
P. D. Altland and B. A. Rattner
Tolerance to a 4-h altitude exposure (6,096-8,230 m) was determined in
immature, young, and old male rats. The critical survival thresholds were
8,230 m for immature rats and 7,620 m for young and old rats. Hypothermia
in immature rats was directly related to hypoxic severity. Body weight
loss, elevated plasma corticosterone concentration, and a mean body
temperature of 32.5 degrees C were characteristics of immature rats that
survived at the critical threshold. Body temperature, weight change, and
plasma corticosterone concentration were similar at all altitudes in young
adult and old rats. Plasma enzyme activities were relatively unchanged in
immature rats, but aspartate aminotransferase (EC 2.6.1.1) and lactate
dehydrogenase (EC 1.1.1.27) activities in old rats, in addition to
fructose-diphosphate aldolase (EC 4.1.2.13) activity in young adults, were
initially elevated (P less than 0.05) at the critical survival threshold
(7,620 m). Body temperature and plasma corticosterone (but not plasma
enzyme activities) are important criteria for determining altitude
tolerance of immature rats. However, plasma asparatate aminotransferase and
lactate dehydrogenase activities are more suitable criteria for assessing
tolerance in young adult and old rats.
