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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

Effects of N-isopropyl oxamate on the activity of LDH, content of LD and ATP in the serum of plateau pika. (A) LDH activity in the serum of plateau pika with different treatments. (B) LD content in the serum of plateau pika with different treatments. (C) Inhibition rates of LDH and LD in the serum. Group 1: taking samples when swimming till exhausted with each bilateral biceps femoris of hind legs injected 0.5 mL normal saline; Group 2: taking samples with each bilateral biceps femoris of hind legs injected 0.5 mL normal saline; Group 3: taking samples when swimming till exhausted with each bilateral biceps femoris of hind legs injected 0.5 mL 1mol/L isopropyl oxamate; Group 4: taking samples with each bilateral biceps femoris of hind legs injected 0.5 mL 1 mol/L isopropyl oxamate. All animals were forced to rest for 30 min after injection. Water temperature: 9–10 °C. All data were expressed as mean ± SD; sample size was 10 for each group. The activity of LDH in Group 1–4 were 0.23 ± 0.026 U/mg, 0.23 ± 0.025 U/mg and 0.16 ± 0.009 U/mg and 0.15 ± 0.014 U/mg, respectively; the LD content in Group 1–4 were 51.86 ± 2.23 mmol/g, 41.71 ± 5.04 mmol/g and 32.29 ± 3.76 mmol/g and 18.80 ± 1.97 mmol/g, respectively; the inhibition rates of LDH and LD in the serum were 34.87% and 54.93 %, respectively. ** p < 0.01.
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ijerph-12-09218-f006: Effects of N-isopropyl oxamate on the activity of LDH, content of LD and ATP in the serum of plateau pika. (A) LDH activity in the serum of plateau pika with different treatments. (B) LD content in the serum of plateau pika with different treatments. (C) Inhibition rates of LDH and LD in the serum. Group 1: taking samples when swimming till exhausted with each bilateral biceps femoris of hind legs injected 0.5 mL normal saline; Group 2: taking samples with each bilateral biceps femoris of hind legs injected 0.5 mL normal saline; Group 3: taking samples when swimming till exhausted with each bilateral biceps femoris of hind legs injected 0.5 mL 1mol/L isopropyl oxamate; Group 4: taking samples with each bilateral biceps femoris of hind legs injected 0.5 mL 1 mol/L isopropyl oxamate. All animals were forced to rest for 30 min after injection. Water temperature: 9–10 °C. All data were expressed as mean ± SD; sample size was 10 for each group. The activity of LDH in Group 1–4 were 0.23 ± 0.026 U/mg, 0.23 ± 0.025 U/mg and 0.16 ± 0.009 U/mg and 0.15 ± 0.014 U/mg, respectively; the LD content in Group 1–4 were 51.86 ± 2.23 mmol/g, 41.71 ± 5.04 mmol/g and 32.29 ± 3.76 mmol/g and 18.80 ± 1.97 mmol/g, respectively; the inhibition rates of LDH and LD in the serum were 34.87% and 54.93 %, respectively. ** p < 0.01.

Mentions: When pikas were injected with 1 mL of 1 mol/L N-isopropyl oxamate in hind legs for 30 min, HPLC showed the inhibitor concentration was 0.08 mmol/L in the blood. As shown in Figure 4, at this concentration, LDH-C4 was inhibited by 70% while LDH-A4 and LDH-B4was only slightly inhibited. Decline of exercise tolerance was indicated by decreased swimming time and reduced LDH, LD and ATP in skeletal muscle. Figure 5 describes the average swimming time of Group 1 and Group 3, which was 374 ± 67 s and 284 ± 93 s, respectively. The swimming time of swimming inhibition group pikas was significantly lower than that of swimming control group (p < 0.01). In addition, as shown in Figure 6 and Figure 7, LDH, LD and ATP of the LDH-C4 inhibited group (Group 3 and 4) in skeletal muscle and serum of plateau pikas were also lower than that of non-inhibited group (Group 1 and 2) (p < 0.05, p < 0.01). LDH and LD inhibition rates by N-isopropyl oxamate in the serum were 34.87% and 54.93%, respectively; and those in the skeletal muscle were 37.12%, 66.27% and 32.42% for LDH, LD and ATP, respectively. LD was higher after swimming while ATP was lower. LDH levels were relatively stable throughout the experiment, suggesting that exercise generates lactate and consumes ATP, but does not affect the LDH activity. Together, our results suggest N-isopropyl oxamate down-regulates the activity of LDH-C4, likely influencing energy metabolism and leads to declined exercise tolerance of plateau pikas.


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)

Effects of N-isopropyl oxamate on the activity of LDH, content of LD and ATP in the serum of plateau pika. (A) LDH activity in the serum of plateau pika with different treatments. (B) LD content in the serum of plateau pika with different treatments. (C) Inhibition rates of LDH and LD in the serum. Group 1: taking samples when swimming till exhausted with each bilateral biceps femoris of hind legs injected 0.5 mL normal saline; Group 2: taking samples with each bilateral biceps femoris of hind legs injected 0.5 mL normal saline; Group 3: taking samples when swimming till exhausted with each bilateral biceps femoris of hind legs injected 0.5 mL 1mol/L isopropyl oxamate; Group 4: taking samples with each bilateral biceps femoris of hind legs injected 0.5 mL 1 mol/L isopropyl oxamate. All animals were forced to rest for 30 min after injection. Water temperature: 9–10 °C. All data were expressed as mean ± SD; sample size was 10 for each group. The activity of LDH in Group 1–4 were 0.23 ± 0.026 U/mg, 0.23 ± 0.025 U/mg and 0.16 ± 0.009 U/mg and 0.15 ± 0.014 U/mg, respectively; the LD content in Group 1–4 were 51.86 ± 2.23 mmol/g, 41.71 ± 5.04 mmol/g and 32.29 ± 3.76 mmol/g and 18.80 ± 1.97 mmol/g, respectively; the inhibition rates of LDH and LD in the serum were 34.87% and 54.93 %, respectively. ** p < 0.01.
© Copyright Policy
Related In: Results  -  Collection

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

ijerph-12-09218-f006: Effects of N-isopropyl oxamate on the activity of LDH, content of LD and ATP in the serum of plateau pika. (A) LDH activity in the serum of plateau pika with different treatments. (B) LD content in the serum of plateau pika with different treatments. (C) Inhibition rates of LDH and LD in the serum. Group 1: taking samples when swimming till exhausted with each bilateral biceps femoris of hind legs injected 0.5 mL normal saline; Group 2: taking samples with each bilateral biceps femoris of hind legs injected 0.5 mL normal saline; Group 3: taking samples when swimming till exhausted with each bilateral biceps femoris of hind legs injected 0.5 mL 1mol/L isopropyl oxamate; Group 4: taking samples with each bilateral biceps femoris of hind legs injected 0.5 mL 1 mol/L isopropyl oxamate. All animals were forced to rest for 30 min after injection. Water temperature: 9–10 °C. All data were expressed as mean ± SD; sample size was 10 for each group. The activity of LDH in Group 1–4 were 0.23 ± 0.026 U/mg, 0.23 ± 0.025 U/mg and 0.16 ± 0.009 U/mg and 0.15 ± 0.014 U/mg, respectively; the LD content in Group 1–4 were 51.86 ± 2.23 mmol/g, 41.71 ± 5.04 mmol/g and 32.29 ± 3.76 mmol/g and 18.80 ± 1.97 mmol/g, respectively; the inhibition rates of LDH and LD in the serum were 34.87% and 54.93 %, respectively. ** p < 0.01.
Mentions: When pikas were injected with 1 mL of 1 mol/L N-isopropyl oxamate in hind legs for 30 min, HPLC showed the inhibitor concentration was 0.08 mmol/L in the blood. As shown in Figure 4, at this concentration, LDH-C4 was inhibited by 70% while LDH-A4 and LDH-B4was only slightly inhibited. Decline of exercise tolerance was indicated by decreased swimming time and reduced LDH, LD and ATP in skeletal muscle. Figure 5 describes the average swimming time of Group 1 and Group 3, which was 374 ± 67 s and 284 ± 93 s, respectively. The swimming time of swimming inhibition group pikas was significantly lower than that of swimming control group (p < 0.01). In addition, as shown in Figure 6 and Figure 7, LDH, LD and ATP of the LDH-C4 inhibited group (Group 3 and 4) in skeletal muscle and serum of plateau pikas were also lower than that of non-inhibited group (Group 1 and 2) (p < 0.05, p < 0.01). LDH and LD inhibition rates by N-isopropyl oxamate in the serum were 34.87% and 54.93%, respectively; and those in the skeletal muscle were 37.12%, 66.27% and 32.42% for LDH, LD and ATP, respectively. LD was higher after swimming while ATP was lower. LDH levels were relatively stable throughout the experiment, suggesting that exercise generates lactate and consumes ATP, but does not affect the LDH activity. Together, our results suggest N-isopropyl oxamate down-regulates the activity of LDH-C4, likely influencing energy metabolism and leads to declined exercise tolerance of plateau pikas.

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