Impact of hibernation on endogenous carbon monoxide concentrations and
heme oxygenase activity in thirteen lined ground squirrels ( Ictidomys
tridecemlineatus )
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Abstract
The thirteen-lined ground squirrel ( Ictidomys tridecemlineatus )
experiences periods of torpor in winter months that are associated with
reduced body temperature, metabolism, and a significant decrease in heart
rate that leads to blood flow reduction [ischemia (I)] to certain tissues.
Between torpor events, brief arousals are shown by increased body
temperature, metabolic rate, and reperfusion (R) to tissues. These I/R
events cause damage in most mammalian tissues, but low to moderate levels of
carbon monoxide (CO) have been shown to alleviate injuries in tissues
exposed to frequent I/R events. High concentrations of endogenously produced
CO have also been reported in the blood and tissues of deep-diving mammals
that routinely experience I/R in their tissues. Heme oxygenase (HO) enzymes
break down heme, producing CO as a byproduct. We examined CO concentrations
and HO activity in tissues from 15 squirrels experiencing consecutive torpor
for 1, 3, 4, or 10 days. Lung CO concentrations after 1 day of torpor (8.2 ±
2.3 pmol/mg) increased after 10 days in torpor (14.9 ± 5.2 pmol/mg).
Conversely, HO activity in the lung on day 1 of torpor (10.2 ± 2.6
nmol/hr/g) decreased after 10 days in torpor (3.6 ± 1.2 nmol/hr/g). The
spleen, an organ involved in erythrocyte turnover, had the highest average
CO content among tissues (29.9 ± 7.0 pmol/mg), though values decreased with
increased time in torpor (16.9 ± 8.2 pmol/mg). Similarly, HO activity in the
spleen was highest in day 1 of torpor (13.5 ± 4.4 nmol/hr/g) and decreased
with increased time spent in torpor (11.6 ± 3.7 nmol/hr/g). These findings
are the first to report variations in CO and corresponding HO activity in
hibernating mammals, providing insight into the physiological significance
of this cytoprotective gas during hibernation.1. NSF Grant (#1927616) 2. Hozier Undergraduate Research Fellowship
2024-2025 3. UNCW Bio and Marine Bio Travel Grant 4. UNCW CSURF Supplies
Grant Summer 2023 and Fall 2024This abstract was presented at the American Physiology Summit 2025 and
is only available in HTML format. There is no downloadable file or PDF
version. The Physiology editorial board was not involved in the peer review
process.
