Saddleback Journal of Biology - Saddleback College

Spring 2010 Biology 3B Paper
which include muscular exhaustion and fatigue. The
short time it takes to reach exhaustion in lizards
makes them prime subjects for a study on the
proposed effect of a glutamine injection.
Materials and Methods
Animal Care
Eleven S. occidentalis, were caught on
March 18, 2010 in Mission Viejo, CA. The lizards
were housed in a glass aquarium in a desert
environment, simulating their natural habitat. A
fluorescent light with a full-spectrum bulb was kept
outside the environment, maintaining a temperature
of 30-35 ºC. Large crickets were fed to the lizards
every two to three days and water was given ad
libitum. Food was withheld 24 hours prior to
experimentation.
Experimentation and Injection Protocol
Measurements were made on various days
between March 23, 2010 and April 2, 2010. For the
trials, the weight of each lizard was recorded. The
lizards were then placed on a treadmill and ran until
exhaustion. Exhaustion was determined as the
inability to overcome the righting reflex for 15
seconds. In this case the righting reflex is the
tendency to bring the body to normal position after
the lizard was placed on its dorsal aspect. The lizards
were allowed to rest at least 24 hours between trials.
The lizards were then given intraperitoneal
injections of glutamine at a dosage of 2.5 g•kg -1 using
a 30-gauge needle (BD Micro-Fine TM IV). The
solution was adjusted to 300 mOSM using NaCl.
Four different trials were conducted. The first trial
was a run without the glutamine injection. For the
other three trials, the lizards were injected with the
appropriate amount of glutamine and were allowed to
metabolize the amino acid for a specific amount of
time, ten, twenty, or thirty minutes respectively.
Results
Exhaustion was seen in S. occidentalis after
intense exercise on the treadmill. As shown in Figure
1, the mean time to exhaustion was normalized for
each lizard’s mass. The mean mass specific time to
reach exhaustion for the lizards after receiving no
injection was 16.85 ± 1.48 sec•g -1 (± S.E.M.). For
trials when the glutamine was allowed to metabolize
for a specific amount of time, ten, twenty, or thirty
minutes, the mean mass specific times to reach
exhaustion were 16.59 ± 0.91 sec•g -1 , 23.60 ± 1.07
sec•g -1 , and 19.25 ± 0.96 sec•g -1 (± S.E.M.)
respectively. A repeated-measure ANOVA was
conducted and showed a significant difference
(p=0.0042, n=11). Completion of the Bonferroni
post-hoc test showed a significant difference between
the twenty minute post injection and every other
condition.
Mean Mass Specific TIme to Exhaustion
(sec/gram)
30
25
20
15
10
5
0
No Injection 10 minutes 20 minutes 30 minutes
Figure 1. Mean mass specific time to reach
exhaustion. Conditions are post injection. Error bars
indicate ± S.E.M.
Discussion
The results of this experiment showed that
there was a significant difference in exhaustion rates
when S. occidentalis received an injected glutamine
load. These results indicate that when glutamine is
allowed to metabolize in the lizard’s system over a
certain time interval, the time to exhaustion is
prolonged. Figure 1 shows that after ten minutes the
glutamine has not produced enough bicarbonate to
buffer the lactate accumulation. The time it took to
reach exhaustion in this case was not significantly
different than the trial with no injection. The results
also indicated that for high performance twenty
minutes was the optimal time to allow the glutamine
to metabolize. After thirty minutes, the effects of the
glutamine begin to decline.
In our previous study, a glutamine injection
was given to seven Green Anole lizards. The lizards
were not allowed time to metabolize the glutamine
and were run directly after injection. There was no
significant difference shown between the injections
of glutamine and the non injection trials (Palhidai and
Santos, in press). The results were similar to the trials
with no injection and ten minute post injection in the
current study.
Gleeson and Bennett (1982) found that total
anaerobic lactate production in lizards can account
for up to 90% of total energy produced during
extensive exercise. Anaerobiosis can provide higher
levels of performance, but it can also lead to a variety
of metabolic consequences, some of which include
muscular exhaustion and fatigue. It was also noted
that behaviorally lizards account for this by sprinting
only short distances with breaks between (Gleeson
and Bennett, 1982).
It was also noted that the effectiveness of
glutamine completely depended on this increase in
bicarbonate and thus the buffering capacity. Without
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Saddleback Journal of Biology
Spring 2010