NORMALIZATION OF HYPERGLYCEMIA BY VANADATE OR VANADYL TREATMENT IN DIABETIC RATS - PHARMACOLOGICAL AND TOXICOLOGICAL ASPECTS

Oral vanadate and vanadyl have been reported to improve glucose homeos tasis in streptozotocin-diabetic rats and have been suggested as possi ble therapeutic agents in diabetes mellitus. The purpose of the presen t study was to determine whether the significant reduction in the plas ma glucose levels of vanadium-treated diabetic rats might be the resul t, at least in part, from reduced food and fluid consumption, or the d irect effect of vanadate or vanadyl administration. Diabetes was induc ed in male rats by s.c. streptozotocin injection (60 mg/kg). Diabetic rats were assigned randomly to one of five regimens for 4 weeks: untre ated (controls), vanadate-treated (0.2 mg of sodium metavanadate per m illiliter drinking water), vanadyl-treated (1.1 mg/ml of vanadyl sulfa te trihydrate per milliliter drinking water), and two groups which rec eived daily equal amounts of food and fluid to those ingested the day before by the animals treated with vanadate or vanadyl. As in previous studies, vanadium treatment of diabetic rats decreased the severity o f diabetes evidenced by decreased hyperphagia, polydipsia, plasma gluc ose levels, and relatively normal weight gain. However, blood glucose levels in the pair-fed rats were always similar to those in the vanadi um-treated diabetic groups. These results would suggest that the ''pos itive'' effects of vanadium therapy on the normalization of hyperglyce mia in STZ-diabetic rats may be secondary to the decreases observed in food and fluid intake. Although the antidiabetic action of vanadate a nd vanadyl has been clearly shown, the results of the present study to gether with the data of previous investigations showing toxic effects of vanadium, would argue out of the use of inorganic vanadium in diabe tes treatment.