Effect of different treatments in calcium-free medium on basal tone and contractile responses of guinea pig tracheae.
Acetylcholine (ACh; 0.1 mmol/l) and KCl (80 mmol/l) induce a biphasic contractile response in isolated guinea pig tracheae maintained at 37 degrees C either in the presence or absence of extracellular Ca2+. Exposure of the tissue to Ca(2+)-free solution evokes a significant decrease in basal tone and the sources of Ca2+ appear to be decreased by prolonged agonist stimulation, and even more by successive agonist stimulation. After an incubation period of 20 min in Ca(2+)-containing solution, the response is restored. Mg(2+)-depletion in Ca(2+)-free medium increased the contractile response to ACh, but not to KCl, and delayed the tonic component of the next contraction elicited in Ca(2+)-containing solution.
Noguera
M A
MA
Departamento de Farmacología, Universidad de Valencia, Spain.
Chuliá
S
S
Ivorra
M D
MD
D'Ocon
M P
MP
D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002120:Calcium Channel Agonists / Q000494:pharmacology; D006168:Guinea Pigs; D017136:Ion Transport / Q000502:physiology; D008274:Magnesium / Q000494:pharmacology*; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology*; D009924:Organ Culture Techniques; D011189:Potassium Chloride / Q000494:pharmacology; D013997:Time Factors; D014132:Trachea / Q000187:drug effects* / Q000502:physiology
D002120:Calcium Channel Agonists; D011189:Potassium Chloride; D008274:Magnesium; D000109:Acetylcholine; D002118:Calcium