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1. Calcium channel currents were recorded in Cs+-dialysed voltage-clamped single smooth muscle cells isolated from the guinea-pig taenia caeci to evaluate the current-carrying ability of Ca2+, Ba2+, Sr2+ and Mg2+ ions. 2. Ba2+ and Sr2+ ions, as well as Ca2+ ions, were able to carry an inward current through calcium channels. Calcium channel current was not(More)
1. Calcium current (ICa) was studied in single isolated smooth muscle cells of a guinea-pig taenia caeci dialysed with Cs+-containing solution to suppress K+ outward current. 2. With increasing step depolarizations up to +10 mV, acceleration of ICa inactivation was observed. With further increase of step depolarization, ICa inactivation was slowed down. The(More)
A single glass micropipette voltage-clamp technique was used to study a potential-dependent calcium inward current in isolated smooth muscle cells of the guinea-pig taenia caeci. Experiments were performed at 22-24 degrees C. With potassium as the main cation in the pipette solution, a transient inward current appeared in response to a depolarizing pulse,(More)
1. Whole-cell and single-channel current recordings were used to study calcium channels in single smooth muscle cells isolated from guinea-pig coronary artery. Potassium currents were blocked by intracellular Cs+ ions. 2. Whole-cell currents were recorded with 10 mM-barium in the bath. Step pulses of 200 ms from a holding potential of -90 mV activated(More)
Cytoplasmic calcium increments in the absence of sarco (endo) plasmic reticulum function were measured with a low-affinity fluorophore Indo-1FF in single isolated smooth muscle cells from guinea-pig urinary bladder. To evaluate the Ca(2+)-buffering properties of the myoplasm, Ca2+ influx, measured as time integral of the Ica (integral of Ica), was compared(More)
1. Voltage-clamped isolated smooth muscle cells from guinea-pig urinary bladder were studied with 3.6 mM extracellular Ca2+ at 36 degrees C. The fluorescence of the Ca(2+)-sensitive dye Indo-1 was used to monitor the cytosolic calcium concentration ([Ca2+]i) and its changes ([Ca2+]i transient). Fast application of caffeine (10 mM) to the cell was used to(More)
1. Vascular smooth muscle cells were isolated from the coronary artery of the guinea-pig. At 2.5 mM [Ca2+]o and 36 degrees C, whole cell membrane currents were recorded under voltage-clamp and the concentration of ionized calcium in the cytoplasm ([Ca2+]i) was monitored by indo-1 fluorescence. 2. At -60 mV, [Ca2+]i was 143 +/- 36 mM (mean +/- S.D.) and was(More)
The rise in free cytosolic calcium was studied by a combination of the techniques of microspectrofluorometry and whole-cell patch clamp. By comparing the membrane currents with their effect on [Ca2+]c, the relative importance of Ca2+ influx could be quantified for both L-type Ca2+ channels and non-selective channels activated by extracellular ATP.
1. Increments in cytosolic Ca2+ concentration (delta[Ca2+]c) were measured in single smooth muscle cells from guinea-pig coronary artery together with the density of peak Ca2+ currents (ICa) in response to clamp steps from -50 to 0 mV. The comparison of depolarization- with caffeine-induced delta[Ca2+]c was used to define the efficacy by which ICa can(More)
1. Whole-cell Ca2+ channel currents were studied in myocytes isolated from guinea-pig circumflex coronary artery at 36 degrees C and with 10 mM-Ba2+ (or Ca2+) as charge carrier. With 180 ms clamp steps from the holding potential of -100 mV, currents at -30 mV were carried mostly through the T-type calcium channels while at positive potentials currents were(More)