Effects of Li-substitution on high-K induced contractions of various smooth muscle tissues in the guinea-pig.
The effects of partial Li-substitution for external Na in the medium on contraction, cellular Li concentration, and 45Ca uptake of various smooth muscle tissues depolarized by a high-K (62.7 mM) solution were studied. In the taenia coli and ileum isolated from the guinea-pig, Li-substitution (23.7 mM-59.4 mM) increased the cellular Li concentration and strongly inhibited the K-contraction. A good correlation between cellular Li concentration and inhibition of tension was obtained in both the taenia coli and ileum. In the portal vein and uterus, Li-substitution inhibited K-concentration in correlation with Li-accumulation although the inhibitory effect was weaker than those obtained with the taenia coli and ileum. In the aorta, Li-substitution did not affect K-concentration in spite of the accumulation of Li. The inhibitory effects of Li-substitution in all the tissues except the aorta were antagonized by an increase in external Ca, and the inhibition was accompanied by a decrease in cellular 45Ca content. Although there is a tissue-specific difference, a possibility exists that excess cellular Li inhibits the K-induced Ca influx. The K-induced Ca influx in the aorta seems to be almost insensitive to the inhibitory effect of cellular Li.
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002132:Calcium Radioisotopes; D005260:Female; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008094:Lithium / Q000494:pharmacology*; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects; D011188:Potassium / Q000494:pharmacology*; D014700:Verapamil / Q000494:pharmacology
D002132:Calcium Radioisotopes; D008094:Lithium; D014700:Verapamil; D011188:Potassium; D002118:Calcium