title: Rabbit intestinal smooth muscle calcium current in solutions with physiological calcium concentration.
abstract: The calcium channel current in enzymatically isolated cells of the longitudinal muscle of rabbit jejunum was studied using the whole-cell voltage clamp technique. The current-voltage relationship was measured in cells held at potentials ranging from -90 to -30 mV in the presence of 1.5 mM-calcium or barium in order to test for the presence of multiple current components. The kinetics and current-voltage relationship of the current showed no evidence of a discrete low-threshold or 'transient' current. Measurable current was observed at -55 mV. Current availability was dependent on the holding potential but not on the test potential, suggesting the presence of only one type of calcium channel. A component of current persisted for at least 25 s following depolarization. Nifedipine reduced the Ca2+ current amplitude without shifting the current-voltage relationship; the degree of inhibition was enhanced by depolarization of the holding potential. The peak and sustained currents were similarly inhibited by nifedipine. The results indicate the presence of a single type of dihydropyridine-sensitive calcium channel current which is partially activated at or near the physiological resting membrane potential of these cells.
authors.affiliation: Division of Pharmacology and Toxicology, UMDS, St Thomas's Hospital, London.
authors.forename: P I
authors.initials: PI
authors.lastname: Aaronson
authors.forename: S N
authors.initials: SN
authors.lastname: Russell
mesh_terms: D000818:Animals; D001464:Barium / Q000502:physiology; D002118:Calcium / Q000502:physiology*; D015220:Calcium Channels / Q000502:physiology; D004594:Electrophysiology; D005260:Female; D007583:Jejunum / Q000502:physiology; D008297:Male; D008564:Membrane Potentials / Q000502:physiology*; D009130:Muscle, Smooth / Q000502:physiology*; D011817:Rabbits
chemical_list: D015220:Calcium Channels; D001464:Barium; D002118:Calcium