Silver-induced frog skeletal muscle contraction and its modulation by calcium antagonists nifedipine and felodipine and calcium agonist Bay K 8644.
1. Ag+ induces one phase of a transient contracture in frog skeletal muscle (0.3-10 microM) and potentiates twitch tension when the fiber is given continuous stimulation. 2. The potentiation of fiber contraction by Ag+ is similar to the effect of Ca2+ antagonists nifedipine and felodipine. 3. Bay K 8644 (100 nM) potentiates and accelerates Ag(+)-induced tension development and the inactivation occurs more rapidly than in the control (Ag+ alone). 4. Two factors can be considered to be essential for the induction of Ag+ contracture: (1) a certain number of Ag+ ions must bind to free SH groups of the voltage sensor; and (2) the binding must occur within a limited time to raise the mechanical threshold to induce contracture. 5. All results suggest that Ag+ binding to crucial SH groups on the Ca2+ channel may be responsible for the activation of muscle contraction, potentiation, and the inhibition of excitation-contraction coupling in skeletal muscle.
Lu
A
A
Department of Veterinary Anatomy and Cellular Biology, Ohio State University, Columbus 43210.
Oba
T
T
Yamano
S
S
Sako
T
T
Yamaguchi
M
M
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology*; D000818:Animals; D004347:Drug Interactions; D015736:Felodipine / Q000494:pharmacology*; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects; D009132:Muscles / Q000187:drug effects*; D009543:Nifedipine / Q000494:pharmacology*; D011896:Rana temporaria; D012834:Silver / Q000494:pharmacology*
D012834:Silver; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D009543:Nifedipine; D015736:Felodipine