Abstract
Sperm specific lactate dehydrogenases (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 testes 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 testes and sperm, but also in the somatic tissues of plateau pika. To reveal the effect of hypoxia on pika Ldh-c expression, we investigated the mRNA and protein level of Ldh-c as well as the biochemical index of anaerobic glycolysis in pika somatic tissues at the altitudes of 2200 m, 3200 m and 3900 m. Our results showed that mRNA and protein expression levels of Ldh-c in the tissues of pika’s heart, liver, brain and skeletal muscle were increased significantly from 2200 m to 3200 m, but had no difference from 3200 m to 3900 m; the activities of LDH and the contents of lactate showed no difference from 2200 m to 3200 m, but were increased significantly from 3200 m to 3900 m. Hypoxia up-regulated and maintained the expression levels of Ldh-c in the pika somatic cells. Under the hypoxia condition, plateau pikas increased anaerobic glycolysis in somatic cells by LDH-C4, and that may have reduced their dependence on oxygen and enhanced their adaptation to the hypoxic environment.
Highlights
The Qinghai-Tibet Plateau, with an average elevation of over 3000 m above sea level, is the highest and largest plateau on earth and it possesses a unique environment of nature and geography.Hypoxia is the most obvious climate characteristic on the plateau, in general; the air content decreases with the elevation at a rate of 0.67 kPa for 100 m, and the average oxygen content on the Qinghai-TibetPlateau is only 60% of that at sea level
We found that the expression levels of Ldh-a and Ldh-b have no statistical difference in skeletal muscle
Our results suggested that at least 27.88% of the ATP in pika skeletal muscle is catalyzed by lactate dehydrogenase (LDH)-C4 by anaerobic glycolysis; pika has a reduced dependence on oxygen and enhanced adaptation to hypoxic environments due to increased anaerobic glycolysis by LDH-C4 in the skeletal muscle
Summary
The Qinghai-Tibet Plateau, with an average elevation of over 3000 m above sea level, is the highest and largest plateau on earth and it possesses a unique environment of nature and geography.Hypoxia is the most obvious climate characteristic on the plateau, in general; the air content decreases with the elevation at a rate of 0.67 kPa for 100 m, and the average oxygen content on the Qinghai-TibetPlateau is only 60% of that at sea level. The Qinghai-Tibet Plateau, with an average elevation of over 3000 m above sea level, is the highest and largest plateau on earth and it possesses a unique environment of nature and geography. Hypoxia is the most obvious climate characteristic on the plateau, in general; the air content decreases with the elevation at a rate of 0.67 kPa for 100 m, and the average oxygen content on the Qinghai-Tibet. Over long-term evolution, many plateau-native animals have developed their own unique mechanisms to adapt to the hypoxic environment on the plateau. Plateau pika (Ochotona curzoniae), an endemic species of the Qinghai-Tibet Plateau, inhabit meadows at altitudes 3000–5000 m above sea level. The pika is a key species in that it plays an important role in the biodiversity of the ecosystem on the Qinghai-Tibetan Plateau [2,3]. Pika fossil samples found on the north edge of the Qinghai-Tibet Plateau are about 37 million years old [4]
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