ARF-independent inhibition of the carbachol-induced contractions by brefeldin A in intestinal smooth muscle.
The aim of this study was to determine whether an ADP ribosylation factor (ARF)-regulated pathway is involved in the carbachol-induced contraction in rat intestinal smooth muscle. Brefeldin A, a known inhibitor of the guanine nucleotide exchange activity on ARF, reversibly inhibited the carbachol-induced contraction in intact ileal muscle strips, whereas the carbachol- and guanosine 5'-O-(3-thiotriphosphate)-induced increases in the Ca2+ sensitivity of myofilaments in beta-escin-permeabilized strips were not affected. The high-K(+)-induced contraction in intact strips was also inhibited by brefeldin A. In isolated ileal myocytes, brefeldin A inhibited the Ca2+ channel current, indicating that the inhibitory effect of brefeldin A in intact cells is related to an inhibition of voltage-dependent Ca2+ channels. Furthermore, the loading of permeabilized strips with the combination of the recombinant fully myristoylated ARF1, the guanine nucleotide exchange factor ARNO, and guanosine 5'-triphosphate did not change the tone at constant pCa (6.45) and did not modify the carbachol- and guanosine 5'-O-(3-thiotriphosphate)-induced Ca2+ sensitization. Taken together, these findings suggest that an ARF-dependent pathway is not involved in the carbachol-induced contraction.
Loirand
G
G
Institut de Pharmacologie Moléculaire et Cellulaire, Centre National de la Recherche Scientifique-Unité Propre de Recherche 411, Valbonne, France.
Cario-Toumaniantz
C
C
Chardin
P
P
Pacaud
P
P
D020823:ADP-Ribosylation Factor 1; D020727:ADP-Ribosylation Factors; D000818:Animals; D020126:Brefeldin A; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000502:physiology*; D002217:Carbachol / Q000494:pharmacology*; D003517:Cyclopentanes / Q000494:pharmacology*; D019204:GTP-Binding Proteins / Q000037:antagonists & inhibitors* / Q000502:physiology; D020690:GTPase-Activating Proteins; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D007082:Ileum / Q000187:drug effects / Q000502:physiology*; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology*; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D003517:Cyclopentanes; D020690:GTPase-Activating Proteins; C102474:cytohesin-2; D020126:Brefeldin A; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D002217:Carbachol; D019204:GTP-Binding Proteins; D020823:ADP-Ribosylation Factor 1; D020727:ADP-Ribosylation Factors