Effect of calcium-channel blockers and salbutamol on the isolated mare uterus--interaction with the calcium agonist Bay K 8644.
The effects of nifedipine, verapamil and diltiazem were investigated in the isolated mare uterus in comparison with salbutamol. All the calcium-channel blockers and salbutamol inhibited the spontaneous, KC1- and electrically induced contractions; nifedipine and salbutamol were the most potent compounds. The calcium agonist Bay K 8644 (10(-8)-10(-6) mol/l) competitively antagonized the inhibitory effect of nifedipine (pA2 value = 8.54 +/- 0.06), whereas it was only slightly or totally ineffective against verapamil, diltiazem and salbutamol. These results indicate that calcium-channel blockers are potent inhibitors of mare uterine motility in vitro and emphasize the importance of Ca2+-related mechanisms in the control of uterine smooth-muscle contractility. Moreover, the validity of Bay K 8644 as a tool to distinguish classes of calcium-channel antagonists is confirmed.
Coruzzi
G
G
Institute of Pharmacology, Faculty of Veterinary, University of Parma, Italy.
Poli
E
E
Bertaccini
G
G
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology*; D000420:Albuterol / Q000494:pharmacology*; D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D004110:Diltiazem / Q000494:pharmacology; D004347:Drug Interactions; D005260:Female; D006736:Horses / Q000502:physiology*; D009543:Nifedipine / Q000494:pharmacology; D014590:Uterine Contraction / Q000187:drug effects; D014599:Uterus / Q000187:drug effects* / Q000502:physiology; D014700:Verapamil / Q000494:pharmacology
D002121:Calcium Channel Blockers; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D014700:Verapamil; D004110:Diltiazem; D009543:Nifedipine; D000420:Albuterol