Effect of Mn2+ on the development of tension induced in guinea-pig taenia coli by Bay K 8644.
We have studied the effects of Mn2+ on the contractile response induced by Bay K 8644, a dihydropyridine Ca2+ agonist, on guinea-pig taenia coli. Mn2+ (5 mM) completely inhibited Bay K 8644 (10(-6) M)-induced rhythmic contraction and contracture to baseline values in normal Ca2+ medium; thereafter, the contraction progressively increased to about 90% of the K+ (60 mM)-induced tonic response. In Ca2+-free medium in the presence of Bay K 8644 Mn2+ also evoked contraction and a concomitant increase in Mn2+ influx into the cytoplasm. These results suggest that during the opening of voltage-dependent Ca2+ channels activated by Bay K 8644, Mn2+ can enter cytoplasm through the channels and induce contraction in taenia coli.
Nasu
T
T
Department of Veterinary Pharmacology, Faculty of Agriculture, Yamaguchi University, Japan.
Sasaki
M
M
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002120:Calcium Channel Agonists / Q000494:pharmacology*; D003106:Colon / Q000187:drug effects* / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007537:Isometric Contraction / Q000187:drug effects; D008297:Male; D008345:Manganese / Q000378:metabolism / Q000494:pharmacology*; D011188:Potassium / Q000494:pharmacology
D002120:Calcium Channel Agonists; D008345:Manganese; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D011188:Potassium; D002118:Calcium