Actions of Mn(2+) in the presence of ionophore A23187 in taenia coli of guinea-pig.
In this work, we have investigated whether Mn(2+)enters the cytoplasm in the presence of ionophore for divalent cations, A23187 and induces contraction of taenia coli. In Ca(2+)-free, 60 m m K(+)medium, the application of 5 m m Mn(2+)evoked contraction and a concomitant increase in Mn(2+)influx into the cytoplasm. However, in Ca(2+)-free medium, the application of 5 m m Mn(2+)in the presence of 1x10(-5)m A23187 did not evoke both contraction and Mn(2+)influx. These results suggest that Mn(2+)penetrates through Ca(2+)channels in a state of membrane depolarization with K(+)and activates the contractile proteins in taenia coli. However, Mn(2+)does not enter the cytoplasm in the presence of ionophore A23187 and then does not induce contraction.
Nasu
T
T
Department of Veterinary Pharmacology, Faculty of Agriculture, Yamaguchi University, Yamaguchi, 753, Japan.
Magami
G
G
D000818:Animals; D000001:Calcimycin / Q000494:pharmacology*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D003106:Colon / Q000187:drug effects* / Q000378:metabolism; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007476:Ionophores / Q000494:pharmacology*; D008297:Male; D008345:Manganese / Q000378:metabolism / Q000494:pharmacology*; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism; D009543:Nifedipine / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology
D002121:Calcium Channel Blockers; D007476:Ionophores; D000001:Calcimycin; D008345:Manganese; D009543:Nifedipine; D011188:Potassium