Vanadium Compounds on Biological Systems Cellular Growth, Oxidation-Reduction Pathways, and Enzymes

1 VANADIUM COMPOUNDS ON BIOLOGICAL SYSTEMS CELLULAR GROWTH, OXIDATION-REDUCTION PATHWAYS, AND ENZYMES 

Characteristics of biological systems, coupled with the rich chemistry of vanadium in aqueous solutions, make the study of effects of vanadium compounds in living systems difficult. The cell is divided into different organelles and vesicles by mem- 

It has been demonstrated that the distribution of vanadium species inside the cell can depend on the form in which the vanadium is administered, as was seen in fish where a different distribution of vanadium in red blood cells (RBCs) was found depending upon whether metavanadate or decavanadate was given. In contrast to this, a similar accumulation was found in plasma and cardiac cytosol. However, the ratio of vanadium in plasma to vanadium in RBCs increased over time with metavanadate administration and remained constant for decavanadate administration. When either of the vanadium compounds was used, most of the vanadium was first found in plasma before moving into the mitochondrial fraction [9,10], Although one can know with some certainty what vanadium compound is given to an animal or put into a tissue culture growth medium, it is difficult to always know the identity of the active form inside the cell. 

Because biological systems are highly susceptible to strong experimental variation, it is difficult to compare the effects of added vanadium compounds in studies from different laboratories. It is difficult to design an experiment that can unequivocally differentiate the effectiveness of two different vanadium compounds. These problems have frequently hampered studies of the antidiabetic properties of vanadium compounds using the noninbred Wistar rat strain in which genetic variability of each animal must be added to the list of biological variables. 

Extrapolating from well-characterized enzymatic inhibition in test tubes, numerous mechanistic ideas concerning the in vivo effects of vanadium compounds have been advanced. The effects of vanadium compounds as transition-state analogs of certain enzymes with a phosphoprotein intermediate in their reaction scheme is proposed to account for the action of vanadium [11] in many biological systems. Unfortunately, it is often difficult to determine if the inhibition observed in the test tube occurs in vivo. For example, although vanadate is a potent inhibitor of plasma membrane ion pumps (such as the sodium potassium ATPase) in the test tube, it is difficult to determine if these pumps are actually inhibited in animals exposed to vanadium compounds. Currently, the role of vanadium compounds as protein phosphatase (PTP) inhibitors is believed to be related to the metabolic effects of this 

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