Two types of Ca(2+)-channels in cells from the circular layer of guinea-pig ileum.
In this paper data are presented concerning some morphometrical characteristics and passive electrical properties of cell membranes from the circular layer of guinea-pig ileum (CC). The main purpose of the study has been to analyze the inward calcium current in these cells. Using the whole-cell voltage-clamp method the presence of T-like type of calcium channels (conducting low-threshold, fast inactivated, strictly potential-dependent and dihydropyridine-resistant calcium inward current--If) could be found in membranes of the cells investigated. The participation of If in the total inward current of CC was deduced from the presence of a low-threshold "hump" in the current-voltage relation curve (I/V-curve) between -80 and -50 mV, and also from a negative shift of this curve at holding potential Vh = -90 mV, compared to the one obtained at Vh = -50 mV. Besides, in the presence of a dihydropyridine Ca2+ antagonist, a fast inactivating component of the inward current could be recorded, which was effectively blocked by 0.3 mmol/l Ni2+ from outside. According to Tsien's criteria (1983) our data suggest the coexistence of T- and L-types calcium channels in CC.
Duridanova
D B
DB
Institute of Physiology, Bulgarian Academy of Sciences, Sofia.
Gagov
H S
HS
Boev
K K
KK
D000818:Animals; D001464:Barium / Q000494:pharmacology; D002104:Cadmium / Q000494:pharmacology; D019256:Cadmium Chloride; D002118:Calcium / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D002712:Chlorides / Q000494:pharmacology; D004553:Electric Conductivity / Q000187:drug effects; D004594:Electrophysiology / Q000379:methods; D005260:Female; D006168:Guinea Pigs; D007082:Ileum / Q000502:physiology*; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009130:Muscle, Smooth / Q000502:physiology*
D015220:Calcium Channels; D002712:Chlorides; D002104:Cadmium; D001464:Barium; D019256:Cadmium Chloride; D002118:Calcium