Inhibitory effect of lithium on muscle contractions caused by various stimulants in guinea-pig ileum.
The tonic contractions induced in the guinea-pig ileal longitudinal muscle by 60 mM KCl, carbachol, histamine or A23187 were inhibited similarly by Li+-substituted solution. There was a good correlation between the Li+-induced inhibition of contractions induced by these stimulants and the intracellularly accumulated Li+ content. In the experiment with fura-2, Li+-substituted solution inhibited the high-K+-induced contraction without decreasing the cytosolic Ca2+ level elevated by high-K+ solution. The concentration-response curve for Ca2+ in the skinned fiber was shifted to the right by pretreatment with Li+-substituted solution. These results suggest that the inhibitory mechanism of Li+ on the contractions by various stimulants partly involves the direct inhibition of the contractile proteins in the guinea-pig ileal longitudinal muscle.
Department of Veterinary Pharmacology, Nippon Veterinary and Zootechnical College, Tokyo, Japan.
M
M
Hori
K
K
Shimizu
S
S
Nakajyo
N
N
Urakawa
D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D006168:Guinea Pigs; D007082:Ileum / Q000187:drug effects; D066298:In Vitro Techniques; D008094:Lithium / Q000494:pharmacology*; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects*
D002217:Carbachol; D008094:Lithium