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The Effect of an Injected Glutamine Load on Time to Exhaustion in Western Fence Lizards
(Sceloporus occidentalis)
Ryan M. Palhidai and Chelsea E. Santos.
Department of Biological Sciences
Saddleback College
Mission Viejo, California 92692
Glutamine is the most abundant amino acid in the human body. It is often
advertised as a nutritional supplement used to increase lactate thresholds prior to exercise.
A study on the effect of a glutamine injection on human lactate accumulation would be
difficult to test. However, lizards require a relatively short time to reach exhaustion, which
is easily observed, making those prime candidates for this study. While lactate accumulates
in muscle and blood of the lizard, muscular function significantly declines. This study was
conducted to test the hypothesis that an injection of glutamine will prolong the exhaustion
caused by lactate accumulation in Western Fence Lizards. The first trail, the control, was a
run without the glutamine injection. The mean weight specific time to reach exhaustion for
the lizards after receiving no injection was 16.85 ± 1.48 sec/gram (± S.E.M.). For the other
three trials, the lizards were injected with a glutamine solution at a dosage of 2.5 g•kg-1
which was adjusted to 300 mOSM using NaCl and then were allowed to metabolize the
amino acid 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/gram, 23.60 ± 1.07 sec/gram, and
19.25 ± 0.96 sec/gram (± S.E.M.) respectively. An injected glutamine load significantly
prolonged exhaustion (p= 0.0042, repeated-measure ANOVA, N=11).
Introduction
Common literature has noted that glutamine,
the most abundant amino acid in the human body,
can be consumed as a nutritional supplement to
increase lactate thresholds prior to exercise. Further
research on the topic has shown that glutamine
increases the concentration of plasma bicarbonate
(Welbourne, 1995). Bicarbonate is produced as byproduct when glutamine is metabolized in the
proximal tubules of the kidney, especially during
times of acidosis. Bicarbonate acts as a well known
buffer system, which buffers lactic acid in the
muscles and blood. It has been shown that sodium
bicarbonate can be taken as a supplement to delay
fatigue during a high intensity workout (McNaughton
et al., 1999). Based on this research, it stands to
reason that an injected load of glutamine will
increase bicarbonate concentrations, prolonging
lactate accumulation, and thus, increasing the time it
takes to reach exhaustion.
Lizards, particularly Western Fence Lizards
(Sceloporus occidentalis), are restricted in their
ability to utilize aerobic metabolism. Instead, they
rely largely upon anerobiosis for rapid creation of
ATP in the muscles. While anaerobiosis can provide
higher levels of performance, it can also lead a
variety of metabolic consequences, some of which
include exhaustion, fatigue, and loss of activity. 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 with a dessert
environment, simulating their natural habitat. A
fluorescent light with a full-spectrum bulb was kept
outside the environment, maintaining a humidity of
60-70%. 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 each
trial, the weight of each lizard was recorded. The
lizards were then placed on the treadmill and ran until
exhaustion. Exhaustion was determined as the
inability to right themselves after 30 seconds when
placed on their backs. The lizards were allowed to
rest at least 24 hours between trials.
The eleven lizards were then given
intraperitoneal injections of glutamine at a dosage of
2.5 g•kg-1 using a 30-gauge needle (BD Micro-FineTM
IV). The solution was adjusted to 300 mOSM using
NaCl. Four different trials were conducted. The first
trail, the control, was a run without the glutamine
injection. For the other three trials, the lizards were
injected with the appropriate amount of glutamine
and then were allowed to metabolize the amino acid
for a specific amount of time, ten, twenty, or thirty
minutes respectively.
Results
Mean Mass Specific TIme to Exhaustion
(sec/gram)
Exhaustion was seen in the Western Fence
Lizards 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/gram (±
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
time to reach exhaustions were 16.59 ± 0.91
sec/gram, 23.60 ± 1.07 sec/gram, and 19.25 ± 0.96
sec/gram (± S.E.M.) respectively. A repeatedmeasure 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.
30
prolonged. The results of this experiment indicated
that twenty minutes was the optimal time to allow the
glutamine to metabolize for highest activity
performance.
Slight variations in the data could be
attributed to weight, activity, and hydration
fluctuations. The time to exhaustion was normalized
for each lizard’s weight, yet there was still a slight
increase in the mean time to reach exhaustion in the
lizards after receiving glutamine injections. Since the
weight increase was accounted for, the variation
could be from a decrease in pre-exercise activity or
an increase in pre-exercise hydration.
In our previous study done last semester, a
glutamine injection was given to seven Green Anole
lizards. The lizards were not allowed time to
metabolize the amino acid. Therefore no significant
difference was shown between the injections of
glutamine and the non injection trials. By allowing
the glutamine to metabolize the lizards were able to
run in longer time intervals.
In a previous study conducted by Welbourne
(1995) indicated that oral glutamine supplementation
increased plasma bicarbonate. It was also noted that
the effectiveness of glutamine completely depended
on this increase in bicarbonate and thus the buffering
capacity.
Literature Cited
Bennett, A.F. and Dawson W.R. (1972). Aerobic and
anaerobic metabolism during activity in the lizard
Dipsosaurus dorsalis. J comp Physiol. Vol. 81: 289299.
Gleeson, T.T., and Bennett A.F. (1982). Acid-base
imbalance in lizards during activity and recovery.
Journal of Experimental Biology. Vol. 98(1): 439453.
25
20
15
10
5
0
No Injection
10 minutes
20 minutes
30 minutes
Figure 1. Mean mass specific time to reach
exhaustion with four different injection conditions.
Conditions are all stated post injection. Error bars
indicate ± S.E.M.
Discussion
The results of this experiment showed that
there was a significant difference in exhaustion rate
when S. occidentalis received an injected glutamine
load. These results indicate that when allowing
glutamine to metabolize in the lizards system over a
certain time interval, the time to exhaustion is
McNaughton, L., Dalton, B., and Palmer, G. (1999).
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Tran, G. and Deleon, E. (2005). Comparisons of
lactate accumulation after extensive exercise and
premature lactate accumulation after lactate injection
in hemidactylus frenatus. Saddleback Journal of
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Wagner, E.L., Scholnick, D.A., and Gleeson, T.T.
(1999). The roles of acidosis and lactate in the
behavioral hypothermia of exhausted lizards. Journal
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Welbourne, T. (1995). Increased plasma bicarbonate
and growth hormone after an oral glutamine load.
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