[Actions of vanadate on muscles].
Vanadate, a trace element of biological tissues and fluid, has been known to be a potent inhibitor of Na, K-ATPase in various tissues. In skeletal muscle, it inhibits the Na, K-ATPase of the membrane fraction, whereas it can not inhibit the Na, K-pump in an intact preparation. It inhibits the Ca-ATPase of the sarcoplasmic reticulum and that of contractile proteins. Vanadate potentiates the contraction of some heart muscles, while it depresses the contraction in some other heart muscles. The positive and negative inotropic effects are mediated by changes in the action potential. The inhibition of Na, K-ATPase is not always involved in the inotropic actions. The inhibition of the Ca-ATPase of the sarcoplasmic reticulum and plasma membrane can be the causes of positive inotropic action. Actions on adenylate cyclase can also be the cause of inotropism. In smooth muscle, vanadate induces contractions with and/or without membrane excitation. The contractions are initiated by both the influx of extracellular Ca2+ and the release of intracellular bound Ca2+. The inhibition of Na, K-ATPase is not involved in the contraction but the inhibition of the Ca-pump of membranous systems can be the cause of the contraction. Vanadate is a useful tool for studies on the excitation-contraction coupling in muscles.
Sunano
S
S
Research Institute of Hypertension, Kinki University, Osaka, Japan.
D000818:Animals; D002118:Calcium / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D055598:Chemical Phenomena; D002621:Chemistry; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects*; D009132:Muscles / Q000187:drug effects; D009200:Myocardial Contraction / Q000187:drug effects*; D012519:Sarcoplasmic Reticulum / Q000201:enzymology; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors*; D014638:Vanadates / Q000494:pharmacology*
D014638:Vanadates; D000252:Calcium-Transporting ATPases; D000254:Sodium-Potassium-Exchanging ATPase; D002118:Calcium