Relationship between vanadate induced relaxation and vanadium content in guinea pig taenia coli

Vanadate has been known to induce a transient increase in high K+ induced contraction, and also gradually relax the high K+ contraction itself in guinea pig taenia coli. The relationship between the rate of relaxation and ion content of Na+, K+, and V ion at the cellular level was investigated when vanadate was applied to contracted muscle. Tissue Na+ and V ion content increased linearly, depending on the time after vanadate treatment, reaching maximum levels of approximately 50 mM·kg-1 and 0.25 mM·kg-1 wet weight, respectively. There was a positive correlation between the V ion and Na+ contents, while there was a negative correlattion between both ions and the relaxed rate of the high K+ induced contraction. The uptake of V ion was affected by the external K+ concentration, and the maximum rate of V ion uptake decreased to 40% in the presence of 90 mM external K+. These results suggest that a small amount of V ion was enough to inhibit the Na+ pump activity and muscle contraction in the high K+ solution.Key words: vanadate, high K+, relaxation, taenia coli, vanadium.