Troponina C na detecção imuno-histoquímica de alterações regressivas precoces no miocárdio de ovinos intoxicados naturalmente por Amaranthus spinosus

Abstract

Amaranthus spp. are nephrotoxic plants popularly known as “pigweed”. When there is poisoning by these plants, the main histopathological alteration is found in the kidneys as toxic tubular nephrosis; however, in some cases, there may be related cardiac changes. ECG changes associated with hyperkalemia have been described in pigs poisoned by Amaranthus retroflexus. Degeneration and necrosis of myocytes have been described in pigs poisoned by A. caudatus and sheep poisoned by A. spinosus. However, there are doubts regarding cardiac changes, since in most cases they are incipient and don’t exhibit inflammatory reaction, which can lead to misinterpretation. For this study, paraffin blocks with tissues from a poisoning outbreak by A. spinosus in southeastern Brazil were used. The objective of the study was to detect the presence of incipient regressive changes in the myocardium of sheep poisoned by A. spinosus using anti-troponin C antibody-based immunohistochemistry. Fragments of hearts from 8 adult sheep and 2 fetuses naturally poisoned by A. spinosus were used. In the immunohistochemistry evaluation of the hearts of the eight adult sheep there were several groups of myocytes with significant decrease or absence of immunoreactivity for anti-troponin C antibody. In most cases, these same areas on Hematoxylin and Eosin (HE) staining exhibited changes that varied from mild cellular tumefaction to increased eosinophilia, as well as loss of striation, cell lysis and karyolysis, sometimes accompanied by mixed inflammatory infiltrate. In four cases, it was possible to notice that several small groups of myocytes exhibiting decreased immunoreactivity corresponded to cells with undetectable or very subtle alterations on HE staining. The hearts of both fetuses did not exhibit areas with loss or decreased immunoreactivity for the anti-troponin C antibody. The results of this immunohistochemical evaluation confirmed the presence of incipient regressive changes and confirmed the occurrence of well-established necrotic lesions in the myocardium of sheep poisoned by Amaranthus spinosus. There was correspondence between areas where immunostaining for troponin was absent and areas with the most marked lesions observed after HE staining. Additionally, the technique was able to detect lesions at a very early stage (myocardial areas with no morphological signs of insult), and demonstrated that the most insulted/injured areas were larger than estimated by observation of HE-stained samples. This study demonstrates the need to better investigate the possible participation of hyperkalemia and other metabolic alterations present in acute renal lesion in the genesis of rapid-onset cardiac lesions, i.e. those not related to vascular lesions caused by long-term uremia.