RESUMO
Effect of acetylcholine (ACh) on Na, K-ATPase system has a complex character. ACh concentration, as well as the type of membrane are responsible for the increase or decrease of Na, K-ATPase activity. The inhibition and activation capacity is not constant in different subcellular fractions. The maximal effect is observed in subcellular fractions rich in junctional complexes, whereas minimal effect is in microsomes. There is no effect in mitochondria and myelin at all. EGTA and EDTA removes the inhibition, but the activation remains unchanged. ACh is supposed to release from membrane structure Ca2+, which subsequently inhibits Na, K-ATPase. On the other hand, activation by ACh is the result of its direct effect. The inhibition prevails over the activation at high (2-10 mM) concentration of ACh, whereas at low (2mM) concentration it might be vice versa. Thus the effect of ACh on Na K-ATPase is the result of two different processes having opposite effects.
