The expression of the sperm-specific lactate dehydrogenase gene Ldh-c in plateau pika (Ochotona curzoniae) cardiac muscle and its effect on the anaerobic glycolysis / 生理学报

The plateau pika (Ochotona curzoniae) has a strong adaptability to hypoxic plateau environment. We found that the sperm-specific lactate dehydrogenase (LDH-C4) gene Ldh-c expressed in plateau pika cardiac muscle. In order to shed light on the effect of LDH-C4 on the anaerobic glycolysis in plateau pika cardiac muscle, 20 pikas were randomly divided into the inhibitor group and the control group, and the sample size of each group was 10. The pikas of inhibitor group were injected with 1 mL 1 mol/L N-isopropyl oxamate, a specific LDH-C4 inhibitor, in biceps femoris muscle of hind legs, each leg with 500 μL. The pikas of control group were injected with the same volume of normal saline (0.9% NaCl). The mRNA and protein expression levels of Ldh-c gene in plateau pika cardiac muscle were determined by real-time PCR and Western blot. The activities of LDH, and the contents of lactate (LD) and ATP in cardiac muscle were compared between the inhibitor group and the control group. The results showed that 1) the expression levels of Ldh-c mRNA and protein were 0.47 ± 0.06 and 0.68 ± 0.08, respectively; 2) 30 min after injection of 1 mL 1 mol/L N-isopropyl oxamate in biceps femoris muscle, the concentration of N-isopropyl oxamate in blood was 0.08 mmol/L; 3) in cardiac muscle of the inhibitor group and the control group, the LDH activities were (6.18 ± 0.48) U/mg and (9.08 ± 0.58) U/mg, the contents of LD were (0.21 ± 0.03) mmol/g and (0.26 ± 0.04) mmol/g, and the contents of ATP were (4.40 ± 0.69) nmol/mg and (6.18 ± 0.73) nmol/mg (P < 0.01); 5) the inhibition rates of N-isopropyl oxamate to LDH, LD and ATP were 31.98%, 20.90% and 28.70%, respectively. The results suggest that Ldh-c expresses in cardiac muscle of plateau pika, and the pika cardiac muscle may get at least 28% ATP for its activities by LDH-C4 catalyzed anaerobic glycolysis, which reduces the dependence on oxygen and enhances the adaptation to the hypoxic environments.

Establishment of RP-HPLC detection method of N-isopropyl oxamate in the serum of plateau pikas / 中国应用生理学杂志

<p><b>OBJECTIVE</b>To explore the intergrating of N-isopropyl oxamate and serum protein and establish a high performance liquid chromatography (HPLC) detection method of N-isopropyl oxamate (specific inhibitor of testis-specific lactate dehydrogenase (LDH-C4)) in the blood of plateau pikas.</p><p><b>METHODS</b>Twenty highland pika 150-200 g, were randomly divided into two groups (n = 10): control group and inhibitor group. Different concentrations of N-isopropyl oxamate were added to examine the intergrating of N-isopropyl oxamate and serum protein. In order to determine its concentration in the pika blood accurately, we used the method of adding trypsin to incubate the serum first, followed by trichloroacetic acid treatment and detecting by HPLC. Results: When the concentrations of N-isopropyl oxamate in the pika serum were added to 0.05 mmol/L, 0.1 mmol/L, 1 mmol/L, 10 mmol/L, 16.7 mmol/L, 33.3 mmol/L and 100 mmol/L, the intergrating rates between N-isopropyl oxamate and plateau pika serum were 100%, 100%, 100%, 86.84%, 54.11%, 40.10% and 20.18%, respectively. The method established in this paper was good on recovery rates, precision and stability. A good linearity was obtained in the range of 0.0125-0.25 mmol/L. When the concentrations of N-isopropyl oxamate in the serum were added to 0. 15 mmol/L,0.3 mmol/L and 1 mmol/L, the recovery rates were 98.05%, 98.98% and 98.12%, respectively; the precision relative standard deviation( RSD) of concentrations were 1.17%, 0.92% and 0.83%, respectively; the stability relative standard deviation (RSD) of concentrations were 1.38%, 1.40% and 0.88%, respectively. The repeatability RSD of the method was 1.76%. Quantitative limit was 0.0125 mmol/L.</p><p><b>CONCLUSION</b>N-isopropyl oxamate has a strong affinity with plateau pika serum protein that can't be accurately determined with common HIPLC method. It can be accurately determined in the blood by adding trypsinto digest the serum protein first, followed by adding trichloroacetic acid to precipitate the protein.</p>