Korean J Physiol Pharmacol.  2000 Dec;4(6):479-486.

The effect of carbon monoxide on contraction, cytosolic Ca2+ level and ionic currents in guinea pig ileal smooth muscle

• Kwon SC
• Chung SS
• Kim YS
• Nam TS

Abstract

The aim of this study was to clarify the mechanism of the inhibitory action of carbon monoxide (CO) on contraction, by measuring cytosolic Ca2+ level ((Ca2+)i) and ionic currents in guinea-pig ileum. CO (10%) inhibited 40 mM KCl-induced contraction and this effect was blocked by ODQ (1 micrometer), a soluble guanylyl cyclase (sGC) inhibitor. CO inhibited the 40 mM KCl-induced contraction without changing (Ca2+)i. Cumulative addition of KCl induced a graded increase in (Ca2+)i and muscle tension. In the presence of CO, cumulative addition of KCl induced smaller contraction than in the absence of CO. On the other hand, the increase in (Ca2+)i induced by cumulative addition of KCl was only slightly decreased in the presence of CO, and the (Ca2+)i-tension relationship shifted downwards. Using the patch clamp technique with a holding potential of -60 mV, we found that CO had little effect on the peak Ba currents (IBa) when voltage was stepped from -60 mV to 0 mV. In addition, CO showed no effect on the depolarization-activated outward K+ currents in the all potential ranges. We conclude that CO inhibits smooth muscle contraction mainly by decreasing the Ca2+ sensitivity of contractile elements via a cGMP-dependent pathway, not by involving L-type Ca2+ and outward-potassium currents in guinea-pig ileum.

Keyword

Carbon monoxide; Intestinal smooth muscle relaxation; cGMP

MeSH Terms

Animals
Carbon Monoxide*
Carbon*
Cytosol*
Guanylate Cyclase
Guinea Pigs*
Guinea*
Hand
Ileum
Muscle Tonus
Muscle, Smooth*
Carbon
Carbon Monoxide
Guanylate Cyclase