Efeitos do extrato bruto da cianobactéria Radiocystis fernandoi no teleósteo, Hoplias malabaricus
Abstract
Eutrophication of the aquatic environment favors cyanobacteria blooms and
affects the biota due to organoleptic water changing and the release of toxins. The
objective of this study was to evaluate the effect of microcystin contained in the
crude extract of the cyanobacteria Radiocystis fernandoi (R28 strain) in the fish
Hoplias malabaricus assessing the degree of structural and functional impairment
of the liver, the accumulation potential in muscle and risk to human health. Traíras
were injected intraperitoneally with 100 μg MC-LReq kg-1 following two
experimental protocols: (i) acute exposure with the application of a single dose of
the crude extract and evaluation after 12 and 96 hours and (II) chronic exposure in
which a dose was injected every 72 hours during 30 days. Genotoxic, biochemical,
physiological and morphological biomarkers were used to evaluate the action of
toxins, structural and ultrastructural damage in the liver, the detoxification
mechanisms and changes in energy metabolism. The R28 strain produced mainly
the MC-RR and MC-YR showing hepatotoxic potential. In the liver there was
accumulation of MC-YR after acute and chronic exposure and MC-RR and MC-RR
only after chronic exposure. There was not MC accumulation in muscle. The
accumulation of the variants (MC-RR and MC-YR) depends on the concentration
and the body's defense system for depuration and biomagnification. Acute and
chronic exposure caused inhibition of the serine protein phosphatase / threonine
type of PP2A activity, increased alanine aminotransferase and aspartate activity
and direct bilirubin in plasma indicating liver damage. Macroscopically occurred
changes in the color, texture and liver mass; microscopically the morphology of
hepatocytes and intracellular organelles were altered and there were dilated
sinusoids and hyperemia. After 30 days, the frequency of changes increase, and
fibrous tissue disrupted the architecture of hepatic tissue. Changes in intermediary
metabolism as glucose, liver glycogen, pyruvate and lactate showed increased
energy demand and physiological stress. Moreover, there was activation of phase
I of the biotransformation system and alterations in cellular antioxidant systems.
Morphological signs of recovery in the liver were observed after 96 hours (single
dose) to MC, but not after 30 days and no signs of cell regeneration. DNA damage
were observed as well. The biochemical changes and liver structure showed
functional impairment of the liver. In conclusion, the microcystin present in the
crude extract of cyanobacteria R. fernandoi (R28 strain) combined with other
substances in the extract may compromise the health and survival of the animal.