Blood glucose alterations induced in rats by canatoxin, a protein isolated from jack bean (Canavalia ensiformis) seeds.

Canatoxin, a lethal convulsant protein isolated from the seeds of Canatoxin ensiformis (jack bean), induced a biphasic alteration in blood glucose levels when injected i.v. into rats and mice. After administration of subconvulsant doses of canatoxin the rats showed initially hyperglycemia during the first 30 min, followed by a long-lasting hypoglycemia. Return to basal glucose levels was not seen up to 15 days. The hyperglycemic effect was dose-dependent and occurred in starved and well-fed animals. A parallelism between convulsant and hyperglycemic activity was observed throughout all canatoxin purification steps. Mice were about 20-fold less sensitive (on a weight basis) than rats to canatoxin-induced hyperglycemia. The hyperglycemic phase was not affected by pretreatment of the rats with alpha- or beta-adrenergic blockers or chlorpromazine, but was potentiated by reserpine and haloperidol. Diazepam and hexamethonium were able to block the hyperglycemic phase of canatoxin's effect. The results suggest that the hyperglycemic alterations induced by canatoxin in rats and mice are probably mediated via the central nervous system.