The potentiation of carbachol-induced transient contractions in guinea-pig stomach muscles by a low temperature.
A transient contraction in guinea-pig stomach muscles was induced by carbachol (CCh, 10(-6) M) in a Ca(2+)-free Krebs solution. This CCh-induced transient contraction (CITC) was remarkable from 22 to 26 degrees C, but not so at other temperatures in most preparations. When a second CCh (10(-6) M) was applied to the tissue with rinsing off CCh 5 min after an application of the first CCh for 10 min, no CITC was observed. The peak amplitude of the CITC increased with the CCh concentration dose-dependently, and that of CITC (by 10(-6) M CCh) declined exponentially over time after washing the tissue with a Ca(2+)-free Krebs solution. The decline time constant increased from 4.8 +/- 1.2 min (mean +/- SEM; n = 5) at 35 degrees C to 13.2 +/- 2.5 min (mean +/- SEM; n = 5) at 22 degrees C. Furthermore, the falling phase of CITC (by 10(-6) M CCh) also showed an exponential decay of 7.4 +/- 0.2 s (mean +/- SEM; n = 6) at 35 degrees C in the time constant. This time constant increased to 22.3 +/- 0.3 s (mean +/- SEM; n = 6) at 22 degrees C. From the above results, it is concluded that CITC may be due to the Ca(2+)-release from an intracellular store site while released Ca2+ may be immediately excluded to an extracellular space by the Ca2+ pump of the plasma membrane, but the Ca2+ pump activity may be reduced and in addition the stored Ca2+ is kept for long time by a low temperature, which thus results in an increase in the amplitude and a prolongation of the falling phase of CITC.
Sakamoto
Y
Y
Department of Physiology, School of Medicine, Fukuoka University, Japan.
Imanaga
I
I
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002217:Carbachol / Q000494:pharmacology*; D003080:Cold Temperature; D004305:Dose-Response Relationship, Drug; D005260:Female; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D009130:Muscle, Smooth / Q000187:drug effects* / Q000502:physiology; D009543:Nifedipine / Q000494:pharmacology; D013270:Stomach / Q000187:drug effects / Q000502:physiology*
D002217:Carbachol; D009543:Nifedipine; D002118:Calcium