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
SaddlebackCollege
Mission Viejo, California92692
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 NaCland 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 by-product 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
ElevenS.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
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 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.
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 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
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