Efeitos da microcistina-LR sobre parâmetros cardiorrespiratórios e biomarcadores do estresse oxidativo de duas espécies de teleósteos neotropicais, traíra, Hoplias malabaricus (Bloch, 1794) e matrinxã, Brycon amazonicus (Spix & Agassiz, 1829)
Resumen
Cyanobacteria, under favorable conditions can form large superficial masses of green
color called blooms. Some genera of cyanobacteria are toxins producers, and during
the bloom, there may be risks of water bodies contamination and thus of those
organisms that depends on this. Among the toxins produced by cyanobacteria, stands
the microcystin. This type of toxin has pronounced effects on the liver, although it can
exhibit its effects in several organs. Moreover, it is the cyanotoxin which is more widely
distributed in various types of ecosystems. In addition to the phosphatases inhibition,
microcystins may also affect DNA repair systems and gene expression, and appear to
interact with the mitochondria of animal tissues leading to oxidative stress and
apoptosis. The aim of this study was to evaluate the cardiorespiratory responses during
graded hypoxia and also the biomarkers of oxidative stress in two species of
Neotropical teleost, traíra, Hoplias malabaricus, and matrinxã, Brycon amazonicus in
control condition and 48 h after of an intraperitoneal injection of lyophilized extract
containing microcystin -LR (MC-LR - 100 μg.Kg-1 body weight). The results indicate
that exposure to MC-LR induced oxidative stress in liver and gills, and changed the
cardiorespiratory responses of both species. In traíra, the exposure to MC-LR
increased PCO2 values, caused hyperventilation, increased metabolic rate, increased
heart rate values and decreased oxygen extraction, it was also observed oxidative
stress in the gill tissue. In matrinxã was observed hyperventilation, increased metabolic
rate and PCO2, and reduction in oxygen extraction. This specie was more sensitive to
the effects of MC-LR, due to the occurrence of oxidative stress in both tissues (gills and
liver), and the death of some animals during the development of graded hypoxia.
Therefore, our results indicate that exposure to MC-LR has harmful effects on the two
species analyzed, both in cardiorespiratory responses, as in the establishment of
oxidative stress, however the magnitude of this effect appears to be species-specific
indicating major susceptibility of the specie Brycon amazonicus to the effect of this
cyanotoxin.