Alternative method for oral administration of insoluble toxins to rats. A prenatal study of L-mimosine.

L-mimosine is a compound found in Leucaena leucocephala, that is used as animal feed due to its high protein content, but it can also cause intoxication. Due to its low solubility in organic and aqueous solvents, its administration in laboratory animals is difficult, especially in delicate periods such as pregnancy. Thus, to circumvent such problems, this study proposes a stress-free form of oral administration with gelatin tablets with flavoring (meat broth) for 14 consecutive days of the gestational period (GD06 to GD20). For that, 17 pregnant Wistar rats divided into 3 groups were used: control (CO; n = 5) not treated; gelatin (GEL; n = 6), which received a gelatin tablet with flavoring; and gelatin with flavoring added 140 mg/kg of L-mimosine (GM; n = 6). All animals received feed and water ad libitum. The parameters analyzed were body weight gain, water and feed consumption, serum biochemistry, blood count and reproductive indices. Among these, only the real and total weight gains of dams showed statistically significant differences, with a decrease in the group GM. Thus, we could observe that flavored gelatin was an efficient and effective administration method to insoluble compounds and long-term administration to pregnant rats, with quick adaptation and without refusal by the animals. In addition, we could observe a direct effect of L-mimosine on the animals' weight gain; however, the dose administered was not sufficient to confer maternal and fetal toxicity.

Assessment of the perinatal effects of maternal ingestion of Ipomoea carnea in rats.

It is believed that Ipomoea carnea toxicosis induces abnormal embryogenesis in livestock. Studies on rats treated with I. carnea aqueous fraction (AF) during gestation, revealed litters with decreased body weight, but the characteristic vacuolar lesions promoted by swainsonine, its main toxic principle, were observed only in young rats on postnatal day (PND) 7. However, these alterations could have resulted as consequence of swainsonine placental passage and/or damage or even ingestion of the contaminated milk by pups. Thus, this perinatal work was performed to verify the transplacental passage of swainsonine and its excretion into milk employing the cross-fostering (CF) procedure as a tool of study. Females were treated with AF or vehicle during gestation and after birth pups were fostered between treated and untreated dams. Pup body weight gain (BWG) and histopathology to observe vacuolar degeneration were performed on PND 3 and 7. In addition, swainsonine detection was performed in amniotic fluid and milk from rats treated with the AF during gestation or lactation. BWG was significantly lower only in pups from mothers treated with the plant and fostered to other treated mothers (AF-AF group of pups). The histopathology revealed that pups from treated mothers fostered to untreated ones showed the characteristic vacuolar lesions; however, the lesions from the AF-AF pups were more severe in both periods evaluated. Amniotic fluid and milk analysis revealed the presence of swainsonine excretion into these fluid compartments. Thus, the results from CF and the chemical analysis allowed concluding that swainsonine passes the placental barrier and affects fetal development and milk excretion participates in I. carnea perinatal toxicosis.

A new exposure model to evaluate smoked illicit drugs in rodents: A study of crack cocaine.

The use of smoked illicit drugs has spread dramatically, but few studies use proper devices to expose animals to inhalational abused drugs despite the availability of numerous smoking devices that mimic tobacco exposure in rodents. Therefore, the present study developed an inexpensive device to easily expose laboratory animals to smoked drugs. We used crack cocaine as the drug of abuse, and the cocaine plasma levels and the behaviors of animals intoxicated with the crack cocaine were evaluated to prove inhaled drug absorption and systemic activity. We developed an acrylic device with two chambers that were interconnected and separated by a hatch. Three doses of crack (100, 250, or 500 mg), which contained 63.7% cocaine, were burned in a pipe, and the rats were exposed to the smoke for 5 or 10 min (n=5/amount/period). Exposure to the 250-mg dose for 10 min achieved cocaine plasma levels that were similar to those of users (170 ng/mL). Behavioral evaluations were also performed to validate the methodology. Rats (n=10/group) for these evaluations were exposed to 250 mg of crack cocaine or air for 10 min, twice daily, for 28 consecutive days. Open-field evaluations were performed at three different periods throughout the experimental design. Exposed animals exhibited transient anorexia, increased motor activity, and shorter stays in central areas of the open field, which suggests reduced anxiety. Therefore, the developed model effectively exposed animals to crack cocaine, and this model may be useful for the investigation of other inhalational abused drugs.

The role of alkaloids in Ipomoea carnea toxicosis: a study in rats.

Ipomoea carnea promotes in livestock a toxicosis histologically characterized by vacuolated cells in different organs. The toxic principles of I. carnea are the alkaloids swainsonine and calystegines B1, B2, B3 and Cl. However, it has not been determined whether the effects observed in rats treated with this plant are only due to swainsonine or if the calystegines have some additive toxic effect. Thus, the aim of the present study was to evaluate in rats the toxic effects of the L carnea aqueous fraction (AF) and of its different alkaloids when administered individually at the same concentration as in this fraction, for 14 days. No anorexic effect and/or alteration in body weight was observed in any group. The histopathologic study showed that while calystegines did not produce any toxic effects, swainsonine and I carnea AF promoted vacuolation in different organs, being more severe in the animals from the I. carnea AF group and extensible to other organs evaluated. No alterations were detected in the central nervous system of rats of any group assayed. The results obtained here suggest that calystegines may act as coadjuvants of swainsonine in I carnea toxicosis; however, little can be proposed about the neurotoxic effect of I. carnea since rats did not prove to be a good model for the reproduction of neuronal storage disease.

Intoxication by Cyanide in Pregnant Sows: Prenatal and Postnatal Evaluation.

Cyanide is a ubiquitous chemical in the environment and has been associated with many intoxication episodes; however, little is known about its potentially toxic effects on development. The aim of this study was to evaluate the effects of maternal exposure to potassium cyanide (KCN) during pregnancy on both sows and their offspring. Twenty-four pregnant sows were allocated into four groups that orally received different doses of KCN (0.0, 2.0, 4.0, and 6.0 mg/kg of body weight) from day 21 of pregnancy to term. The KCN-treated sows showed histological lesions in the CNS, thyroid follicle enlargement, thyroid epithelial thickening, colloid reabsorption changes, and vacuolar degeneration of the renal tubular epithelium. Sows treated with 4.0 mg/kg KCN showed an increase in the number of dead piglets at birth. Weaned piglets from all KCN-treated groups showed histological lesions in the thyroid glands with features similar to those found in their mothers. The exposure of pregnant sows to cyanide thus caused toxic effects in both mothers and piglets. We suggest that swine can serve as a useful animal model to assess the neurological, goitrogenic, and reproductive effects of cyanide toxicosis.

Zearalenone, an estrogenic mycotoxin, is an immunotoxic compound.

The aim of this study was to assess the toxic effects of zearalenone (ZEA) on the immune function. Ovariectomised rats were treated daily by gavage with 3.0 mg/kg of ZEA for 28 days. Body weight gain, food consumption, haemotological parameters, lymphoid organs, and their cellularities were evaluated. Moreover, acquired immune responses and macrophage activity were also assessed. ZEA promoted reduction in body weight gain, which is not fully explained by diminished food consumption. Despite no effect on haematological parameters, ZEA caused thymic atrophy with histological and thymocyte phenotype changes and decrease in the B cell percentage in the spleen. With respect to acquired and innate immune responses, no statistically significant differences in delayed-type hypersensitivity were noticed; however, in the ZEA-treated rats, antibody production and peroxide release by macrophages were impaired. The observed results could be related to ZEA activity on ERs; thus, ZEA is an immunotoxic compound similar to estrogen and some endocrine disruptors.

The immunomodulatory effects of Ipomoea carnea in rats vary depending on life stage.

Ipomoea carnea Jacq. ssp. fistulosa (Mart. Ex Choisy; Convolvulaceae; I. carnea) possesses a toxic component: an indolizidine alkaloid swainsonine (SW) that has immunomodulatory effects due to its inhibition of glycoprotein metabolism. It is also known that SW is excreted into both the amniotic fluid and milk of female rats exposed to I. carnea. Thus, the aim of this study was to determine whether SW exposure, either in utero or from the milk of dams treated with I. carnea, modulates offspring immune function into adulthood. In addition, adult (70 days old) and juvenile rats (21 days old) were exposed to I. carnea in order to evaluate several other immune parameters: lymphoid organs relative weight and cellularity, humoral and cellular immune responses. Offspring exposed to I. carnea during lactation developed rheumatoid arthritis (RA) in adulthood after an immunogenic challenge. In addition, both adult and juvenile rats exposed to I. carnea showed discrepancies in several immune parameters, but did not exhibit any decrease in humoral immune response, which was enhanced at both ages. These findings indicate that SW modulates immune function in adult rats exposed to SW during lactation and in juvenile and adult rats exposed to SW as juveniles and adults, respectively.

Haematological and immunological effects of repeated dose exposure of rats to integerrimine N-oxide from Senecio brasiliensis.

This study is the first in the literature to focus attention on the possible immunotoxic effect of integerrimine N-oxide content in the butanolic residue (BR) of Senecio brasiliensis, a poisonous hepatotoxic plant that contains pyrrolizidine alkaloids (PAs). PAs have been reported as a pasture and food contaminant and as herbal medicine used worldwide and are responsible for poisoning events in livestock and human beings. After the plant extraction, BR extracted from Senecio brasiliensis was found to contain approximately 70% integerrimine N-oxide by elemental and spectral analyses ((1)H and (13)C NMR), which was administered to adult male Wistar Hannover rats at doses of 3, 6 and 9 mg/kg for 28 days. Body weight gain, food consumption, lymphoid organs, neutrophil analysis, humoural immune response, cellular immune response and lymphocyte analysis were evaluated. Our study showed that integerrimine N-oxide could promote an impairment in the body weight gain, interference with blood cell counts and a reducing T cell proliferative activity in rats; however, no differences in the neutrophil activities, lymphocytes phenotyping and humoural and cellular immune responses were observed. It is concluded that doses of integerrimine N-oxide here employed did not produce marked immunotoxic effects.

Increased antitumor efficacy by the combined administration of swainsonine and cisplatin in vivo.

Swainsonine is a natural α-mannosidase inhibitor found in numerous poisonous plants, such as Astragalus lentiginosus. Its mechanism of action is through the inhibition of Golgi α-mannosidase II activity in the N-glycan biosynthesis pathway. As a result, swainsonine inhibits the production of complex ß1,6-branched N-linked glycans, which are related to the malignant phenotype of tumor cells. In this study, we investigated whether treatment with swainsonine affects the sensitivity of Ehrlich ascites carcinoma (EAC) cells to cisplatin. To this end, male C57BL/6 mice were treated with swainsonine (SW--0.5 mg/kg, i.p., twice-daily for ten days) and/or cisplatin (Cis--0.25 mg/kg, i.p., every other day for a total of five applications) two days after transplantation with EAC cells. The results showed a greater reduction in the ascites volume in mice from the CisSW group (63.5%) than in mice from the Cis group (45.7%), an elevated induction of apoptosis by CisSW treatment when compared to Cis alone, as demonstrated by higher percentage of cells in the subG1 phase in that group (p<0.0001 Kruskal-Wallis, p<0.0001 control vs. CisSW, p<0.001 Co vs. Cis post-test Dunn), and an increase in the median survival from 12.5 days observed in the control group to 27 days in the CisSW group, which corresponds to a 116% survival increase (p=0.0022 Co vs. CisSW Log-rank test). In addition, the mice from the Cis group had a median survival of only 15 days, an increase of just 20% compared to controls. Our results indicate that swainsonine increases the sensitivity of EAC cells to cisplatin.

Low doses of monocrotaline in rats cause diminished bone marrow cellularity and compromised nitric oxide production by peritoneal macrophages.

Monocrotaline (MCT) is a pyrrolizidine alkaloid found in a variety of plants. The main symptoms of MCT toxicosis in livestock are related to hepato- and nephrotoxicity; in rodents and humans, the induction of a pulmonary hypertensive state that progresses to cor pulmonale has received much attention. Although studies have shown that MCT can cause effects on cellular functions that would be critical to those of lymphocytes/macrophages during a normal immune response, no immunotoxicological study on MCT have yet to ever be performed. Thus, the aim of the present study was to evaluate the effect of MCT on different branches of the immune system using the rat--which is known to be sensitive to the effects of MCT--as the model. Rats were treated once a day by gavage with 0.0, 0.3, 1.0, 3.0, or 5.0 mg MCT/kg for 14 days, and then any effects of the alkaloid on lymphoid organs, acquired immune responses, and macrophage activity were evaluated. No alterations in the relative weight of lymphoid organs were observed; however, diminished bone marrow cellularity in rats treated with the alkaloid was observed. MCT did not affect humoral or cellular immune responses. When macrophages were evaluated, treatments with MCT caused no significant alterations in phagocytic function or in hydrogen peroxide (H2O2) production; however, the MCT did cause compromised nitric oxide (NO) release by these cells.