title: Otilonium bromide inhibits calcium entry through L-type calcium channels in human intestinal smooth muscle.
abstract: Otilonium bromide (OB) is used as an intestinal antispasmodic. The mechanism of action of OB is not completely understood. As Ca(2+) entry into intestinal smooth muscle is required to trigger contractile activity, our hypothesis was that OB blocked Ca(2+) entry through L-type Ca(2+) channels. Our aim was to determine the effects of OB on Ca(2+), Na(+) and K(+) ion channels in human jejunal circular smooth muscle cells and on L-type Ca(2+) channels expressed heterologously in HEK293 cells. Whole cell currents were recorded using standard patch clamp techniques. Otilonium bromide (0.09-9 micromol L(-1)) was used as this reproduced clinical intracellular concentrations. In human circular smooth muscle cells, OB inhibited L-type Ca(2+) current by 25% at 0.9 micromol L(-1) and 90% at 9 micromol L(-1). Otilonium bromide had no effect on Na(+) or K(+) currents. In HEK293 cells, 1 micromol L(-1) OB significantly inhibited the expressed L-type Ca(2+) channels. Truncation of the alpha(1C) subunit C and N termini did not block the inhibitory effects of OB. Otilonium bromide inhibited Ca(2+) entry through L-type Ca(2+) at concentrations similar to intestinal tissue levels. This effect may underlie the observed muscle relaxant effects of the drug.
authors.affiliation: Enteric NeuroScience Program, Mayo Clinic, Rochester, MN 55905, USA.
authors.forename: P R
authors.initials: PR
authors.lastname: Strege
authors.forename: S
authors.initials: S
authors.lastname: Evangelista
authors.forename: G L
authors.initials: GL
authors.lastname: Lyford
authors.forename: M G
authors.initials: MG
authors.lastname: Sarr
authors.forename: G
authors.initials: G
authors.lastname: Farrugia
mesh_terms: D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D015220:Calcium Channels / Q000187:drug effects; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000187:drug effects*; D043183:Irritable Bowel Syndrome / Q000188:drug therapy; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009130:Muscle, Smooth / Q000187:drug effects* / Q000378:metabolism; D009924:Organ Culture Techniques; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology*; D015222:Sodium Channels / Q000187:drug effects / Q000502:physiology
chemical_list: D002121:Calcium Channel Blockers; D015220:Calcium Channels; D015221:Potassium Channels; D000644:Quaternary Ammonium Compounds; D015222:Sodium Channels; C013934:octylonium; D002118:Calcium