Potential toxic effects produced by L-mimosine in the thyroid and reproductive systems. Evaluation in male rats.

Leucaena leucocephala is a worldwide plant used as forage; however, its use in animal production has been limited because of the presence of a toxic nonprotein amino acid, L-mimosine. L-mimosine exhibits negative effects not only in ruminants but also in monogastric animals; however, there is little information available on the effect of this amino acid in monogastric species. Thus, this study aimed to evaluate the general toxicity of L-mimosine in rats, as well as its effects on the endocrine and reproductive systems. L-mimosine was extracted from seeds of L. leucocephala that were administered orally by gavage to adult Wistar rats at different doses of 25, 40 and 60 mg/kg body weight/day for 28 days. The following parameters were evaluated: weight gain, feed intake, serum enzymes, histopathology (liver, kidney, thyroid, thymus, and spleen), serum hormones (testosterone, corticosterone, T3 and T4) and sexual behavior. No clinical signs of toxicity were observed in animals, but histopathology revealed consistent lesions in the thyroids. Additionally, rats exposed to L-mimosine presented low serum levels of testosterone, decreased mount numbers and increased mount intervals. Therefore, our study reinforces the assumption that L-mimosine has goitrogenic potential and causes impairment in male reproductive performance.