Sex-related canatoxin-induced blood glucose alterations in the rat

The present study was designed to characterize sex-related canatoxin-induced blood glucose alterations in rats. Chronic administration of canatoxin (50 mU, ip, daily for 3 days) induced hypoglycemia in female rats (N = 6) (-36.54 + or - 3.24%, P<0.05). The response of pregnant rats (N = 8) was similar to that observed for male rats (+29.57 + or - 4.70%). Administration of canatoxin did not modify blood glucose levels of gonadectomized male or female rats. Similarly, pretreatment of intact male or female rats with human chorionic gonadotropin (40 IU/kg, im) blocked the effect of canatoxin on blood glucose levels. Gonadal steroid replacement (testosterone, 10 mg/kg,im) for gonadectomized male rats did not reverse the inhibition of canatoxin-induced blood glucose alterations, whereas pretreatment of intact female rats (N = 6) with tetosterone (10 mg/kg, im) significantly attenuated the canatoxin-induced hypoglycemia. These data indicate that the blood glucose alterations produced by canatoxin in rats are under hormonal regulation

Effect of canatoxin on the circulating levels of gonadotropins and prolactin in rats

1. The effects of canatoxin, the toxic principle from Canavalia ensiformis seeds which has lipoxygenase-activating properties, were evaluated in rats using radioimmunoassay techiniques to measure plasma levels of prolactin (PRL), progesterone, follicle stimulating (LH) and luteinizing (LH) hormones. 2. The chronic administration of canatoxin (50, 100 or 200 microng/Kg daily for 12 days, ip) to female rats induced a sharp rise in plasma LH and FSH concentrations whit no changes in progesterone level. A fall in circulating PRL was also observed. The frequency of proestrus and weight gain increased in rats treated with the higest dose of toxin used, but there was no alteration in weight of uterus or ovaries. 3. The increases in gonadotropin levels with canatoxin are consistent with the lipoxygenase-activating properties of the toxin, but do not explain why plasma PRL concentrations decreased in canatoxin-treated rats. 4. Since the animals in the control group had high PRL and low LH levels and since canatoxin increased LH and decreased PRL in the circulation, a possible stress-prevention effect is discussed for the toxin. 5. This study supports previous suggestions of central actions for canatoxin, and indicates the hypophysis and/or hypothalamus as one of the target sites for the toxin in the central nervous system

Convulsions induced by canatoxin in rats are probably a consequence of hypoxia

Canatoxin, a convulsant neurotoxin from the seeds of Canavalia ensiformis, induces lipoxygenase-dependent hypoxia and sex-related alterations of carbohydrate metabolism in rats which are blocked by glucose, diazepam and hexamethonium. The present study analyzes the possible causal relationship between the convulsant action of canatoxin and its effects on carbohydrate metabolism. The incidence of canatoxin-induced convulsions was greater in male than in female rats. Pretreatment of male rats with drugs that block hypoxia, such as glucose (2.5 g/kg,iv,15 min), diazepam (5 mg/kg,ip, at 48 h, 24 animals against convulsions, respiratory distress and death. These results suggest that canatoxin/induced convulsions are probably the consequence of hypoxia and both effects are mediated by lipoxygenase activation