Changes in lactate dehydrogenase and malate dehydrogenase activities during hypoxia and after temperature acclimation in the armored fish, Rhinelepis strigosa (Siluriformes, Loricariidae)

Abstract

Lactate (LDH) and malate dehydrogenase (MDH) of white skeletal muscle of fishes acclimated to 20, 25 and 30 degrees C and thereafter submitted to hypoxia were studied in different substrate concentrations. Significant differences for LDH and MDH of white muscle enzyme activities are described here for the first time in Rhinelepis strigosa of fishes acclimated to 20 degrees C and submitted to hypoxia for six hours. LDH presented a significant decrease in enzyme affinity for pyruvate in acute hypoxia, for fishes acclimated to 20 degrees C and an increase for fishes acclimated to 30 degrees C.

Aerobic and anaerobic enzyme activity in the hake Merluccius gayi gayi related to the Oxygen Minimum Zone off central-southern Chile

“…This support the predominance of aerobic metabolism in all the tissues except muscle, agreeing with other studies carried out on fish (Childress & Somero 1979, Yang et al 1992, Panepucci et al 2000, Panepucci et al 2001, Treberg et al 2003 and most vertebrates (Hochachka & Somero 1973).…”

“…In contrast, white muscle shows very low levels of MDH activity, which suggests that M. gayi gayi adjusts its metabolism toward efficient anaerobic production of ATP and the use of LDH to maintain cytoplasmic NAD/NADH (Chippari-Gomez et al 2003). This is also observed in the different MDH/LDH ratios between tissues, where white muscle showed the lowest, while brain and heart both had ratios higher than 1, indicating that attenuated pyruvate to lactate flux is produced in these tissues and, as a consequence, carbohydrate metabolism will be largely channelled toward complete oxidation (Almeida-Val & Hochachka 1995 sensu Panepucci et al 2000). These results agree with Panepucci et al (2000), who found an extremely high MDH/LDH ratio for the heart of the fish Rhinelepis strigosas, showing the importance of this organ to fish survival in critically hypoxic situations.…”

“…MDH activities in the liver, brain, and heart were very similar, revealing a potential anaerobic metabolism in these organs under prolonged periods of low-oxygen conditions, preventing lactic acid accumulation (Shapiro & Bobkova 1975, Panepucci et al 2000. In contrast, white muscle shows very low levels of MDH activity, which suggests that M. gayi gayi adjusts its metabolism toward efficient anaerobic production of ATP and the use of LDH to maintain cytoplasmic NAD/NADH (Chippari-Gomez et al 2003).…”

Time Course Studies on Impact of Low Temperature Exposure on the Levels of Protein and Enzymes in Fifth Instar Larvae of Eri Silkworm, Philosamia ricini (Lepidoptera: satuniidae)

“…Earlier it has been reported that some organisms, when subjected to low temperature stress, exhibited a marked alteration in their metabolism by changing the levels of certain enzyme(s) activity [3,5,18,19]. In present study, we have shown that the level of total protein content increases consistently in hemolymph of Eri silkworm insect larvae due to low temperature stress over increasing period of exposure.…”

“…Some studies have been conducted to study the acclimation of various organisms to low temperature and hypoxic conditions in order to understand the role of few intermediary metabolites and enzymes. The enzymes concerned with energy metabolism can be divided into three groups, those related to anaerobic metabolism, aerobic metabolism and the pentose phosphate pathway [5]. However, studies are required to understand the role of energy metabolism enzymes in insects including Eri silkworm exposed to low temperature [6].…”