Estudo de indicadores de estresse em Brycon amazonicus (matrinxã) exposto a deltametrina (Keshet®)
Abstract
In the last 40 years, the use of pesticides increased 700% in Brazil, setting
this country into the very consumers of this kind of chemicals in the world. There
among the most used pesticides in Brazil are the pyrethroids, a class of insecticides
largely used for the stability to light rays and being not accumulated in the trophic
chain. Deltamethrin is a pyrethroid classified as moderately toxic and it may work
as endocrine disruptor. It is widely used in the farms and preserving stocked foods.
Pyrethroids are low toxic to mammals and birds. Although, new studies pointed
out their noxiousness to aquatic organisms such as fishes. The high toxicity of
pyrethroids to fishes may be related to damages caused to nervous system and to
their mechanisms of biochemical degradation. Biomarkers are a way of monitoring
the pesticides effects on the environments. Among them, cholinesterases and
metabolites such as glucose, cortisol and lactate can be used. In the present
monography is reported a work carried out in vivo with matrinxa exposed to
deltamethrin (Keshet®) at 20, 40 and 60% of CL50:96h for 96 hours, and other in
vitro with matrinxa exposed to the analytical formulation of deltamethrin
(Pestanal®). After the pesticide exposure, fish were anesthetized, blood was
withdrawn and then the fish were killed for brain, liver, gut, gills and white muscle
excision. From the observations we can say that glucose, protein and ammonia
were increased in liver, and amino acids and ammonia were increased in plasma.
The glycogen bulks of liver and plasma lactate were decreased. In white muscle,
protein and amino acids levels were decreased, and ammonia, glucose and lactate
increased. Concerning the studied enzymes, it was observed inhibition of brain
AChE in vivo and in vitro activities while CbE was inhibited in the gills and gut but
increased in white muscle and plasma. The enzyme activities of ALAT and ASAT
increased in liver and LDH activity was reduced. Therefore, we may conclude that
matrinxa presented metabolic changes in order to supply the energetic demand
caused by deltamethrin poisoning. The inhibition of AChE was observed, as
expected, in addition to CbE increase, showing the activation of mechanisms to
degrade deltamethrin. It is possible to assert that Brycon amazonicus exposed to
deltamethrin is biochemically responsive to the poisoning using adaptive
strategies which enable it to escape from toxic effects of a contaminated
environment by such xenobiotic.