Aspectos clínico-patológicos e laboratoriais da intoxicação experimental por monofluoroacetato de sódio em ovinos

Abstract

Sodium monofluoracetate (MF) has been isolated from several plants in South Africa and Australia, as well as in Brazil from three (Palicourea marcgravii, Arrabidaea bilabiata and, probably from Mascagnia rigida) of the 12 plants that cause "sudden death" in cattle. MF blocks the Krebs cycle and the production of ATP. The death is due to the most intense effect either on the heart, SNC, or both, depending on the poisoned animal species. In 1959, Döbereiner and Tokarnia detected hydropic-vacuolar degeneration (HVD) of the distal convoluted uriniferous tubules, associated with nuclear picnosis, a lesion they considered typical for the poisoning by P. marcgravii. Furthermore, it was seen that this alteration also appears in the kidney of cattle poisoned by all the other Brazilian sudden death causing plants (BSDCP). The objective of this study was to verify if the ingestion of single doses of MF and daily quantities of 1/2.5 and 1/5 of the lethal dose in six sheep causes the same lesion in the kidney of cattle poisoned by BSDCP. This would prove that MF is responsible for the death of animals which ingest these plants. MF was administered orally in single doses of 0.5 and 1.0 mg/kg to four animals, and repeated daily doses of 0.1 and 0.2 mg/kg to two animals. Death occurred in five of six animals. The course of the poisoning lasted from 3 min. to 33h 5 min. Clinically the animals presented palpitation, abdominal breathing, slight balance loss with sometimes swaying gait, the animals laid down and placed the head on their flank. In the “dramatic phase”, all the animals fell into lateral decubitus, stretched out the legs, made peddling movements, presented opistotonus, and died. The electrocardiographical examination showed heart dilatation and reduction of the systolic shortening fraction. Laboratory hematological exams revealed increased urea and creatinine. MF caused the clinical and pathological symptoms of “sudden death”. At postmortem examination, heart auricles and jugular, cava, azygos and pulmonary veins of all animals were moderately ingurgitaded, and in some sheep, pulmonary edema was observed. Histopathology revealed HVD of the epithelial cells of the distal convoluted uriniferous tubules associated with nuclear picnosis in all animals. Vacuolation and less often necrosis of liver cells was seen in some cases. No references on that peculiar type of lesion could be found in the literature, exception the description of kidney lesions in animals associated with the ingestion of BSDCP, and recent studies of MF poisoning in cattle. HVD has been observed animals that develop toxic tubular nephrosis; however, in these cases, this lesion is not restricted to the distal kidney tubules and does not occur with nuclear picnosis. The present study demonstrated in sheep that single lethal doses or repeated doses of fractions of the lethal doses of MF causes HVD of the distal convoluted uriniferous tubules, associated with nuclear picnosis. This confirms that this compound is the toxic principle responsible for the death of animals poisoned by BSDCP.