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Testis-Specific Lactate Dehydrogenase (LDH-C4) in Skeletal Muscle Enhances Apika's Sprint-Running Capacity in Hypoxic Environment.

Wang Y, Wei L, Wei D, Li X, Xu L, Wei L - Int J Environ Res Public Health (2015)

Bottom Line: In this study, the effects of N-propyl oxamate and N-isopropyl oxamate on LDH isozyme kinetics were compared to screens for a selective inhibitor of LDH-C4.Our results suggested that ldh-c is expressed in the skeletal muscle of plateau pika, and at least 32.42% of ATP in the skeletal muscle is catalyzed by LDH-C4 by anaerobic glycolysis.This suggests that pika has reduced dependence on oxygen and enhanced adaptation to hypoxic environment due to increased anaerobic glycolysis by LDH-C4 in skeletal muscle.

View Article: PubMed Central - PubMed

Affiliation: Research Center for High Altitude Medicine, Qinghai University, Xining 810016, China. yangwangmd@163.com.

ABSTRACT
LDH-C4 is a lactate dehydrogenase that catalyzes the conversion of pyruvate to lactate. In mammals, ldh-c was originally thought to be expressed only in testis and spermatozoa. Plateau pika (Ochotona curzoniae), which belongs to the genus Ochotona of the Ochotonidea family, is a hypoxia tolerant mammal living 3000-5000 m above sea level on the Qinghai-Tibet Plateau, an environment which is strongly hypoxic. Ldh-c is expressed not only in testis and sperm but also in somatic tissues of plateau pika. In this study, the effects of N-propyl oxamate and N-isopropyl oxamate on LDH isozyme kinetics were compared to screens for a selective inhibitor of LDH-C4. To reveal the role and physiological mechanism of LDH-C4 in skeletal muscle of plateau pika, we investigated the effect of N-isopropyl oxamate on the pika exercise tolerance as well as the physiological mechanism. Our results show that Ki of N-propyl oxamate and N-isopropyl oxamate for LDH-A4, LDH-B4, and LDH-C4 were 0.094 mmol/L and 0.462 mmol/L, 0.119 mmol/L and 0.248 mmol/L, and 0.015 mmol/L and 0.013 mmol/L, respectively. N-isopropyl oxamate is a powerful selective inhibitor of plateau pika LDH-C4. In our exercise tolerance experiment, groups treated with inhibitors had significantly lower swimming times than the uninhibited control group. The inhibition rates of LDH, LD, and ATP were 37.12%, 66.27%, and 32.42%, respectively. Our results suggested that ldh-c is expressed in the skeletal muscle of plateau pika, and at least 32.42% of ATP in the skeletal muscle is catalyzed by LDH-C4 by anaerobic glycolysis. This suggests that pika has reduced dependence on oxygen and enhanced adaptation to hypoxic environment due to increased anaerobic glycolysis by LDH-C4 in skeletal muscle. LDH-C4 in plateau pika plays the crucial role in anaerobic glycolysis and generates ATP rapidly since this is the role of LDH-A4 in most species on plain land, which provide evidence that the native humans and animals in Qinghai-Tibet plateau can adapt to the hypoxia environment.

No MeSH data available.


Related in: MedlinePlus

Effect of pyruvate on the inhibitory activity of N-propyl oxamate and N-isopropyl oxamate on plateau pika LDH-B4. Reciprocal values of V were calculated taking the reciprocal values of Δ340 nm/min, plots of reciprocal reaction velocity versus reciprocal pyruvate concentration at a constant NADH concentration. The concentrations of pyruvate used were 0.1 mmol/L, 0.2 mmol/L, 0.4 mmol/L, 0.6 mmol/L, and 0.8 mmol/L. NADH concentration was kept at 0.15 mmol/L. The Km of LDH-B4for pyruvate was 0.172 mmol/L. (◆) assays with 0 mmol/L, (■) 0.01 mmol/L, (▲) 0.02 mmol/L, (×) 0.04 mmol/L and (●) 0.08 mmol/L of N-propyl oxamate or N-isopropyl oxamate. Upper left: determination of Ki from replot of slope values against inhibitor concentrations. The Ki of N-propyl oxamate and N-isopropyl oxamate for LDH-B4 were 0.119 mmol/L and 0.248 mmol/L, respectively.
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ijerph-12-09218-f002: Effect of pyruvate on the inhibitory activity of N-propyl oxamate and N-isopropyl oxamate on plateau pika LDH-B4. Reciprocal values of V were calculated taking the reciprocal values of Δ340 nm/min, plots of reciprocal reaction velocity versus reciprocal pyruvate concentration at a constant NADH concentration. The concentrations of pyruvate used were 0.1 mmol/L, 0.2 mmol/L, 0.4 mmol/L, 0.6 mmol/L, and 0.8 mmol/L. NADH concentration was kept at 0.15 mmol/L. The Km of LDH-B4for pyruvate was 0.172 mmol/L. (◆) assays with 0 mmol/L, (■) 0.01 mmol/L, (▲) 0.02 mmol/L, (×) 0.04 mmol/L and (●) 0.08 mmol/L of N-propyl oxamate or N-isopropyl oxamate. Upper left: determination of Ki from replot of slope values against inhibitor concentrations. The Ki of N-propyl oxamate and N-isopropyl oxamate for LDH-B4 were 0.119 mmol/L and 0.248 mmol/L, respectively.

Mentions: We purified LDH isozymes from E. coli and characterized how N-propyl oxamate and N-propyl oxamate affected enzyme kinetics, as shown in Figure 1, Figure 2 and Figure 3. Ki of LDH-A4 by N-propyl oxamate and N-isopropyl oxamate was 0.094 mmol/L and 0.462 mmol/L, respectively, shown in Figure 1; Ki of LDH-B4 by N-propyl oxamate and N-isopropyl oxamate was 0.119 mmol/L and 0.248 mmol/L, respectively, shown in Figure 2; Ki of LDH-C4 by N-propyl oxamate and N-isopropyl oxamate was 0.015 mmol/L and 0.013 mmol/L, respectively, shown in Figure 3. Our results indicate the LDH-A4 and LDH-B4 inhibition by N-propyl oxamate is five and two times higher than that of N-isopropyl oxamate, but the Ki of LDH-C4 by the two inhibitors was almost the same. The above results suggest the two inhibitors have different inhibition effects on LDH-A4 and LDH-B4, but were comparable for LDH-C4. N-isopropyl oxamate was more specific for LDH-C4 than N-propyl oxamate at concentrations up to 0.1 mmol/L, as shown in Figure 4. When the concentration of N-isopropyl oxamate was 0.1 mmol/L, LDH-C4 was inhibited by 70% while LDH-A4and LDH-B4 were only inhibited by less than 10%. Therefore, N-isopropyl oxamate was selected as the optimal inhibitor to study the function of LDH-C4 in the exercise tolerance of plateau pikas in the further experiments.


Testis-Specific Lactate Dehydrogenase (LDH-C4) in Skeletal Muscle Enhances Apika's Sprint-Running Capacity in Hypoxic Environment.

Wang Y, Wei L, Wei D, Li X, Xu L, Wei L - Int J Environ Res Public Health (2015)

Effect of pyruvate on the inhibitory activity of N-propyl oxamate and N-isopropyl oxamate on plateau pika LDH-B4. Reciprocal values of V were calculated taking the reciprocal values of Δ340 nm/min, plots of reciprocal reaction velocity versus reciprocal pyruvate concentration at a constant NADH concentration. The concentrations of pyruvate used were 0.1 mmol/L, 0.2 mmol/L, 0.4 mmol/L, 0.6 mmol/L, and 0.8 mmol/L. NADH concentration was kept at 0.15 mmol/L. The Km of LDH-B4for pyruvate was 0.172 mmol/L. (◆) assays with 0 mmol/L, (■) 0.01 mmol/L, (▲) 0.02 mmol/L, (×) 0.04 mmol/L and (●) 0.08 mmol/L of N-propyl oxamate or N-isopropyl oxamate. Upper left: determination of Ki from replot of slope values against inhibitor concentrations. The Ki of N-propyl oxamate and N-isopropyl oxamate for LDH-B4 were 0.119 mmol/L and 0.248 mmol/L, respectively.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4555275&req=5

ijerph-12-09218-f002: Effect of pyruvate on the inhibitory activity of N-propyl oxamate and N-isopropyl oxamate on plateau pika LDH-B4. Reciprocal values of V were calculated taking the reciprocal values of Δ340 nm/min, plots of reciprocal reaction velocity versus reciprocal pyruvate concentration at a constant NADH concentration. The concentrations of pyruvate used were 0.1 mmol/L, 0.2 mmol/L, 0.4 mmol/L, 0.6 mmol/L, and 0.8 mmol/L. NADH concentration was kept at 0.15 mmol/L. The Km of LDH-B4for pyruvate was 0.172 mmol/L. (◆) assays with 0 mmol/L, (■) 0.01 mmol/L, (▲) 0.02 mmol/L, (×) 0.04 mmol/L and (●) 0.08 mmol/L of N-propyl oxamate or N-isopropyl oxamate. Upper left: determination of Ki from replot of slope values against inhibitor concentrations. The Ki of N-propyl oxamate and N-isopropyl oxamate for LDH-B4 were 0.119 mmol/L and 0.248 mmol/L, respectively.
Mentions: We purified LDH isozymes from E. coli and characterized how N-propyl oxamate and N-propyl oxamate affected enzyme kinetics, as shown in Figure 1, Figure 2 and Figure 3. Ki of LDH-A4 by N-propyl oxamate and N-isopropyl oxamate was 0.094 mmol/L and 0.462 mmol/L, respectively, shown in Figure 1; Ki of LDH-B4 by N-propyl oxamate and N-isopropyl oxamate was 0.119 mmol/L and 0.248 mmol/L, respectively, shown in Figure 2; Ki of LDH-C4 by N-propyl oxamate and N-isopropyl oxamate was 0.015 mmol/L and 0.013 mmol/L, respectively, shown in Figure 3. Our results indicate the LDH-A4 and LDH-B4 inhibition by N-propyl oxamate is five and two times higher than that of N-isopropyl oxamate, but the Ki of LDH-C4 by the two inhibitors was almost the same. The above results suggest the two inhibitors have different inhibition effects on LDH-A4 and LDH-B4, but were comparable for LDH-C4. N-isopropyl oxamate was more specific for LDH-C4 than N-propyl oxamate at concentrations up to 0.1 mmol/L, as shown in Figure 4. When the concentration of N-isopropyl oxamate was 0.1 mmol/L, LDH-C4 was inhibited by 70% while LDH-A4and LDH-B4 were only inhibited by less than 10%. Therefore, N-isopropyl oxamate was selected as the optimal inhibitor to study the function of LDH-C4 in the exercise tolerance of plateau pikas in the further experiments.

Bottom Line: In this study, the effects of N-propyl oxamate and N-isopropyl oxamate on LDH isozyme kinetics were compared to screens for a selective inhibitor of LDH-C4.Our results suggested that ldh-c is expressed in the skeletal muscle of plateau pika, and at least 32.42% of ATP in the skeletal muscle is catalyzed by LDH-C4 by anaerobic glycolysis.This suggests that pika has reduced dependence on oxygen and enhanced adaptation to hypoxic environment due to increased anaerobic glycolysis by LDH-C4 in skeletal muscle.

View Article: PubMed Central - PubMed

Affiliation: Research Center for High Altitude Medicine, Qinghai University, Xining 810016, China. yangwangmd@163.com.

ABSTRACT
LDH-C4 is a lactate dehydrogenase that catalyzes the conversion of pyruvate to lactate. In mammals, ldh-c was originally thought to be expressed only in testis and spermatozoa. Plateau pika (Ochotona curzoniae), which belongs to the genus Ochotona of the Ochotonidea family, is a hypoxia tolerant mammal living 3000-5000 m above sea level on the Qinghai-Tibet Plateau, an environment which is strongly hypoxic. Ldh-c is expressed not only in testis and sperm but also in somatic tissues of plateau pika. In this study, the effects of N-propyl oxamate and N-isopropyl oxamate on LDH isozyme kinetics were compared to screens for a selective inhibitor of LDH-C4. To reveal the role and physiological mechanism of LDH-C4 in skeletal muscle of plateau pika, we investigated the effect of N-isopropyl oxamate on the pika exercise tolerance as well as the physiological mechanism. Our results show that Ki of N-propyl oxamate and N-isopropyl oxamate for LDH-A4, LDH-B4, and LDH-C4 were 0.094 mmol/L and 0.462 mmol/L, 0.119 mmol/L and 0.248 mmol/L, and 0.015 mmol/L and 0.013 mmol/L, respectively. N-isopropyl oxamate is a powerful selective inhibitor of plateau pika LDH-C4. In our exercise tolerance experiment, groups treated with inhibitors had significantly lower swimming times than the uninhibited control group. The inhibition rates of LDH, LD, and ATP were 37.12%, 66.27%, and 32.42%, respectively. Our results suggested that ldh-c is expressed in the skeletal muscle of plateau pika, and at least 32.42% of ATP in the skeletal muscle is catalyzed by LDH-C4 by anaerobic glycolysis. This suggests that pika has reduced dependence on oxygen and enhanced adaptation to hypoxic environment due to increased anaerobic glycolysis by LDH-C4 in skeletal muscle. LDH-C4 in plateau pika plays the crucial role in anaerobic glycolysis and generates ATP rapidly since this is the role of LDH-A4 in most species on plain land, which provide evidence that the native humans and animals in Qinghai-Tibet plateau can adapt to the hypoxia environment.

No MeSH data available.


Related in: MedlinePlus