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Title: Controle molecular dos níveis eritrocitários de GTP em Colossoma macropomum (Characiformes, Cuvier 1818) em hipóxia
Authors: Oliveira, Vinícius Faria de
metadata.dc.contributor.advisor: Val, Adalberto Luis
Keywords: Tambaqui
Issue Date: 21-Aug-2017
Publisher: Instituto Nacional de Pesquisa da Amazônia - INPA
metadata.dc.publisher.program: Genética, Conservação e Biologia Evolutiva - GCBEv
metadata.dc.description.resumo: Hypoxia events are common in the aquatic ecosystems of the Amazon. As a result, numerous adaptive adjustments to optimize oxygen uptake are known in the fish of this region, including, but not limited to, increased opercular beats, the release of circulating blood cells, metabolic suppression, and reduction of organic phosphate concentration in erythrocytes. This study aimed to find out how the regulation of the concentration of guanosine triphosphate ([GTP]) occurs in the red cells of tambaqui exposed to hypoxia. GTP by acting as a negative modulator of the affinity of hemoglobin with O 2 decreases oxygen uptake; thus, a reduction of [GTP] in hypoxia represents a strategy to improve the transfer of oxygen to tissues. An important cellular process that may be involved in the reduction of GTP levels in erythrocytes is the synthesis of proteins, specifically the translation stage. At this point there is an element designate eIF2α, which requires GTP to be able to recruit the RNAt Met i and continue the formation of the translation machinery. Thus, we investigated the relative expression of two eIFs (eIF2α and eIF3A) by real-time PCR and quantified the GTP in erythrocytes of tambaqui juveniles exposed to normoxia, four exposures to hypoxia (<1 mgO 2 /L) (30, 140, 200 e 260 min) and recovery from hypoxia (240 e 480 min) in >6.0 mgO 2 /L. Our results showed an increase in the relative expression of the two genes analyzed at practically all times of exposure to hypoxia. eIF2α gene was not elevated relatively to the control group at 30 min only. The concentrations of GTP were sharply reduced until the group exposed to 140 min of hypoxia, remaining practically stable until 480 min of recovery. In this way, we noticed that the decrease in the [GTP] occurred between the 30 and 140 min of hypoxia. We confirmed that Colossoma macropomum specimens were hypoxic by high plasma levels of glucose and lactate of animals subjected to low oxygen availability in water. The increase in the relative expression of the eIFs at the same time as a sharp reduction in the GTP concentration in the tambaqui erythrocytes a relationship between the intensity of the protein synthesis and the consumption of GTP molecules. However, during hypoxia, a severe metabolic suppression occurs to establish a balance between production and consumption of ATP, since the primary source of this compound is compromised. As a consequence an overall decrease in protein synthesis is observed. On the other hand, many genes linked to the mechanisms of hypoxia response are regulated positively, increasing their transcripts in the cell, which, to become functional products, depend on an elevation of the translation rate, even if only transient. This phenomenon contributes to the metabolic reorganization, essential for greater resistance of organisms to hypoxia.
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