The effects of vanadate on cellular Ca2+ movements across the sarcolemma of cardiac muscle cells were investigated by measuring the intracellular and extracellular Ca2+ activities of guinea pig papillary muscle with Ca2+-selective electrodes. During the rest period following a steady-state of 2 contractions per second the extracellular Ca2+ concentration was increased over the basal level within a minute. During the rest period Ca2+ was transported across the sarcolemma into the extracellular space. Vanadate decreased the change in extracellular Ca2+ concentration during the rest period implying that the Ca2+ efflux across the sarcolemma was decreased by vanadate. Vanadate increased intracellular Ca2+ activities significantly (from 1.9 X 10(-7) M to 10(-6)M) resulting in an increase in resting tension. These results suggest that vanadate decreases Ca2+ efflux from the cells into the extracellular space by blocking Ca2+ transport across the sarcolemma, possibly blocking the Na+-Ca2+ exchange transport.
Animal ; Calcium/metabolism* ; Female ; Guinea Pigs ; Ion Channels/drug effects* ; Male ; Membrane Potentials/drug effects ; Papillary Muscles/drug effects* ; Vanadates ; Vanadium/pharmacology*

AIMTo study the hypoglycemic effect of bis (alpha-furancarboxylato) oxovanadium (IV) (VO-FA) in normal rats and streptozotocin (STZ)-diabetic rats.

METHODSRats were injected intraperitoneally STZ 50 mg.kg(-1) to induce diabetes. Blood glucose, glycohemoglobin, glycogen and serum insulin were observed after administering intragastrically VO-FA for four weeks.

RESULTSAfter 2 weeks administration, VO-FA reduced the blood glucose in STZ-rats (P < 0. 01) dose-dependently, and up to 4 weeks the blood glucose was normalized (below 11.1 mmol.L(-1)) in some of STZ-rats, whereas did not decrease in normal rats. After administration of VO-FA at the dosage of 56.8 and 113.6 mg.kg(-1), the serum insulin levels were lowered in normal rats and STZ-rats, respectively. Moreover, VO-FA reduced glycohemoglobin, improved the glucose tolerance, and increased the liver glycogen and muscle glycogen contents in STZ-rats in a dose-dependent manner (P < 0. 05, P < 0. 01), but not in normal rats.

CONCLUSIONVO-FA could improve the glycometabolism in STZ-rats, but not in normal rats.

Animals ; Blood Glucose ; metabolism ; Diabetes Mellitus, Experimental ; blood ; metabolism ; Dose-Response Relationship, Drug ; Glucose Tolerance Test ; Glycated Hemoglobin A ; metabolism ; Hypoglycemic Agents ; administration & dosage ; pharmacology ; Insulin ; blood ; Liver Glycogen ; metabolism ; Male ; Organometallic Compounds ; administration & dosage ; pharmacology ; Random Allocation ; Rats ; Rats, Sprague-Dawley ; Vanadium ; administration & dosage ; pharmacology