Tension inhibitory effect of lead ions and lead uptake in ileal longitudinal muscle of the guinea-pig.
1. In ileal longitudinal smooth muscle of the guinea-pig, lead ions (Pb2+) inhibited the phasic response to high-K+ (60 mM) solution more strongly than the tonic response. 2. Pb2+ displaced Ca2+ concentration-response curves to the right. Moreover, Pb2+ inhibited the 45Ca binding at high affinity sites determined by the La3+ method than low affinity sites during K(+)-induced contraction. 3. After treatment with Pb2+, the tonic tension caused by high-K+ was fairly restored by a wash with normal medium. The lead bound to the muscle cells was almost eliminated after 20-30 min with a normal medium. 4. We suggest that Pb2+ binds loosely to the surface membrane of ileal longitudinal muscle. Pb2+ probably reduced the tension in response to the high-K+ mainly by inhibiting Ca2+ release rather than by affecting Ca2+ influx.
Nasu
T
T
Department of Veterinary Pharmacology, Faculty of Agriculture, Yamaguchi University, Japan.
Suzuki
J
J
Shibata
H
H
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002132:Calcium Radioisotopes; D006168:Guinea Pigs / Q000378:metabolism*; D007082:Ileum / Q000187:drug effects / Q000378:metabolism; D066298:In Vitro Techniques; D007811:Lanthanum / Q000494:pharmacology; D007854:Lead / Q000378:metabolism / Q000494:pharmacology*; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects* / Q000378:metabolism; D011188:Potassium / Q000494:pharmacology; D012964:Sodium / Q000502:physiology
D002132:Calcium Radioisotopes; D007854:Lead; D007811:Lanthanum; D012964:Sodium; D011188:Potassium; D002118:Calcium