Actions of cardiac glycosides (C.G.) on smooth muscles are reviewed.
1. C.G. inhbit the Na-K ATPase of smooth muscle membrane, though the degree and mode of the inhibition vary among the types of smooth muscles.
2. The uptake of C.G. by smooth muscles has been reproted to be influenced by K
+, Na, ATP, and temperature. The difference between the uptake and its effect can be observed.
3. Intracellular K concentration decreased and intracellular Na concentration increased by the treatment with C.G.
4. They depolarized the membrane; the action being affected by extracellular ion concentration. An increase in spike discharges is observed.
5. C.G. potentiate or inhibit the contractions of smooth muscles, depending on the types of smooth muscles and the causes of the contraction. C.G. can also cause transient contraction of smooth muscle.
6. C.G. influence the Ca content and Ca movements of smooth muscles.
7. C.G. cause the release of noradrenaline, acetylcholine, or prostaglandins.
These substances can affect the contractile responses of smooth muscles.
抄録全体を表示