In mammalian hibernators, metabolism varies dramatically between deep hibernation and
arousal. This change is reflected in tissue glycolytic and oxidative capacities. This thesis
investigated cellular and tissue metabolism in the different stages of hibernation in ground
squirrels.
Total liver ATP content was not different between deep hibernation, arousal, and summer
euthermia. In vivo 31P-NMR spectroscopy showed no change in liver and skeletal muscle high
energy phosphate content during arousal. This observation indicates that metabolism is well
regulated, and ATP consumption must be reduced to a similar degree as ATP production in
hibernation.
I predicted a reduced metabolic rate (Vo2) in hepatocytes isolated from animals in deep
hibernation relative to cells from euthermic squirrels. At 37°C, Vo2 was 20% - 25% higher in
hepatocytes from hibernating, aroused and summer cold acclimated animals than in cells from
summer euthermic controls. Na+/K+ ATPase, considered an important ATP consumer in
mammalian tissues, accounted for only around 15% of cellular Vo2 at 37°C, and this proportion
did not change with hibernation state. When measured at 7°C, no difference in hepatocyte Vo2
was found between hibernation states. A CO2 induced intracellular acidification of 0.1 - 0.2 pH
units did not affect Vo2 at 37°C or 7°C.
I hypothesized that the higher metabolic capacities of hepatocytes from hibernating and
aroused animals may permit higher rates of biosynthetic functions, important during periodic
arousals. At 37°C gluconeogenic rates from lactate/pyruvate were 63% higher in hepatocytes
from hibernating squirrels than those from summer control animals. With glycerol, these rates in
the hibernating, aroused and cold acclimated states were twice that of summer state. No
differences in activities of key gluconeogenic enzymes or oxidative efficiencies between
hibernation states were found. Endogenous rates of ketone body production were higher in
hepatocytes from hibernating S. lateralis, but with 3mM palmitate as substrate, no differences
were evident.
From these studies I conclude that metabolism remains well regulated, balanced and
flexible throughout the hibernation cycle. This unique metabolice organization may permit
energetic savings by allowing for a reduced Vb2 in deep hibernation, and an elevated VO2 during
arousal to support high biosynthetic rates, thereby minimizing arousal durations and their
attendant thermogenic demands. / Science, Faculty of / Zoology, Department of / Graduate
| Identifer | oai:union.ndltd.org:UBC/oai:circle.library.ubc.ca:2429/6205 |
| Date | 05 1900 |
| Creators | Staples, James Francis |
| Source Sets | University of British Columbia |
| Language | English |
| Detected Language | English |
| Type | Text, Thesis/Dissertation |
| Format | 6087946 bytes, application/pdf |
| Rights | For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use. |
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