Inhibitory effects of vanadate on the contractile responses in vascular smooth muscle.
The effects of vanadate (Na3VO4) on the contractions induced by high concentrations of K, histamine and norepinephrine in isolated guinea-pig aorta were investigated. Vanadate (10(-3) M) relaxed the high K contraction only when the external K concentration was above 85.4 mM. Vanadate showed no inhibitory action on the contraction induced by either Na-containing 45.4 mM K solution or Na-poor 45.4 mM K solution. Ouabain (2 X 10(-5) M) had no inhibitory effects on the contractions induced by these high K solutions. Vanadate failed to relax the contraction induced by histamine or norepinephrine in normal (5.4 mM) medium, while it inhibited the contraction in the presence of 142.2 mM K. Ouabain also did not inhibit the histamine- or norepinephrine-induced contraction in either normal or high K solution. These results suggest that the inhibitory actions of vanadate are not due to an inhibition of Na pump and that these effects depend on the presence of a high concentration of external K ions.
D000818:Animals; D006168:Guinea Pigs; D006632:Histamine / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D009638:Norepinephrine / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D012964:Sodium / Q000172:deficiency; D014639:Vanadium / Q000494:pharmacology*
D014639:Vanadium; D006632:Histamine; D012964:Sodium; D011188:Potassium; D009638:Norepinephrine