Manganese ions penetrate via L-type Ca2+ channels and induce contraction in high-K+ medium in ileal longitudinal muscle of guinea-pig.
1. Mn2+ (5 mM) completely inhibited the K+ (10-60 mM)-induced ileal tonic tension to the baseline, however, the tension and Mn2+ uptake increased progressively, depending on the K+ concentration of above 35 mM. 2. The L-type Ca2+ channel blocker, D-600 and nifedipine inhibited the tension development and Mn2+ uptake after addition of Mn2+ in the high-K+ (60 mM) medium, however, T-type Ca2+ channel blocker, Ni2+ and amiloride had no effect on it. 3. D-600 and nifedipine inhibited the tension development and Mn2+ uptake in the presence of 5 mM Mn2+ in the Ca(2+)-free, high-K+ (60 mM) medium. 4. The results suggest that Mn2+ penetrates via L-type Ca2+ channels in the ileal cell membrane in a state of prolonged depolarization and activates the contractile elements.
Nasu
T
T
Department of Veterinary Pharmacology, Faculty of Agriculture, Yamaguchi University, Japan.
Murase
H
H
Shibata
H
H
D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D015220:Calcium Channels / Q000187:drug effects* / Q000378:metabolism; D004347:Drug Interactions; D006168:Guinea Pigs; D007082:Ileum / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D066298:In Vitro Techniques; D007477:Ions; D008297:Male; D008345:Manganese / Q000493:pharmacokinetics / Q000494:pharmacology*; D009119:Muscle Contraction / Q000187:drug effects* / Q000502:physiology; D009130:Muscle, Smooth / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D009532:Nickel / Q000493:pharmacokinetics; D009543:Nifedipine / Q000494:pharmacology; D011188:Potassium / Q000037:antagonists & inhibitors / Q000494:pharmacology
D015220:Calcium Channels; D007477:Ions; D008345:Manganese; D000584:Amiloride; D009532:Nickel; D009543:Nifedipine; D011188:Potassium