Changes in calcium channel current densities in rat colonic smooth muscle cells during development and aging

1993 ◽  
Vol 265 (3) ◽  
pp. C617-C625 ◽  
Author(s):  
Z. Xiong ◽  
N. Sperelakis ◽  
A. Noffsinger ◽  
C. Fenoglio-Preiser
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Reversal Potential ◽  
Muscle Cells ◽  
Peak Current ◽  
Channel Current ◽  
Low Concentrations ◽  
Highly Sensitive ◽  
Current Densities ◽  
Channel Currents

The age-related changes of Ca2+ channel currents were investigated in freshly isolated single smooth muscle cells from the circular layer of the distal colon from the rat using the whole cell voltage clamp technique. Under physiological conditions (Ca2+ concentration of 2.0 mM), the averaged total Ca2+ current density increased markedly from 1.25 pA/pF in the newborn rat to 6.46 pA/pF in the 60-day-old rat; it then gradually declined with aging. Two types of Ca2+ channel currents seemed to be present; one type possessed more negative threshold potentials (-70 to -60 mV) when the cells were held at -80 or -100 mV and inactivated quickly. The voltage for peak current was -20 to -10 mV, and the reversal potential was +60 to +70 mV. This current was highly sensitive to low concentrations of Ni2+ (30 microM) but was resistant to nifedipine, diltiazem, cadmium, and tetrodotoxin. In contrast, the other type of Ca2+ channel current possessed more positive threshold potential (-40 mV) and inactivated more slowly. The voltage for peak current was 0 mV, and the reversal potential was +60 to +70 mV. This current was insensitive to low concentrations of Ni2+ but highly sensitive to nifedipine, diltiazem, and cadmium. These results suggest that the fast inactivating (transient) current might be T-type Ca2+ current [ICa(T)], and such cells were ICa(T) positive cells; whereas the sustained Ca2+ current was L-type Ca2+ current [ICa(L)], and such cells were ICa(L) positive cells. Our results showed that the fraction of ICa(T) positive cells increased with development; the current densities of both ICa(L) and ICa(T) also increased with development.(ABSTRACT TRUNCATED AT 250 WORDS)

Gestational change in Na+ and Ca2+ channel current densities in rat myometrial smooth muscle cells

1991 ◽  
Vol 260 (3) ◽  
pp. C658-C663 ◽  
Author(s):  
Y. Inoue ◽  
N. Sperelakis
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Reversal Potential ◽  
Cell Voltage ◽  
Muscle Cells ◽  
Linear Increase ◽  
Na Channels ◽  
Pregnant Rat ◽  
Spread Of Excitation ◽  
Current Densities

The change of Na+ and Ca2+ channel currents during gestation was investigated using the whole cell voltage-clamp method on single smooth muscle cells freshly isolated from the longitudinal layer of pregnant rat uterus. The current-voltage relationships for both the Na+ and Ca2+ currents did not change during gestation. The threshold voltage, the voltage at the peak inward current, and the reversal potential (extrapolated) were virtually identical. The averaged current densities of Ca2+ channel were almost unchanged between days 9 and 21; this value at day 5 was somewhat lower. In contrast, the averaged current density of fast Na+ channels increased markedly in the myometrium during gestation: from 0 at day 5 to 0.19 +/- 0.16 at day 9, to 0.56 +/- 0.13 at day 14, to 0.90 +/- 0.13 at day 18, and to 0.86 +/- 0.14 pA/pF at day 21. This almost linear increase in the averaged density of fast Na+ channels during gestation occurs because of an increase in the fraction of cells which possessed fast Na+ channels. These results suggest that the role of fast Na+ channels in myometrial activity becomes more and more important as term approaches. We suggest that the fast Na+ current may be involved in spread of excitation.

A Novel Single-Photon Counting Technique Applied to Highly Sensitive Measurement of [Ca2+]i Transient in Human Aortic Smooth Muscle Cells

2006 ◽  
Vol 128 (5) ◽  
pp. 777-781
Author(s):  
Shigeru Tada ◽  
Ken Okazaki
Keyword(s):  
Shear Stress ◽  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Single Photon ◽  
Photon Counting ◽  
Muscle Cells ◽  
Single Photon Counting ◽  
Aortic Smooth Muscle Cells ◽  
Aortic Smooth Muscle ◽  
Highly Sensitive

This study demonstrates that aequorin, a luminescent natural dye, is useful for vascular cell intracellular Ca2+ concentration ([Ca2+]i) determination. A new single-photon counting technique was developed to resolve the effects of fluid flow shear stress on [Ca2+]i in human aortic smooth muscle cells (HASMCs). Confluent HASMCs were grown on petri dishes loaded with aequorin. Then the dishes were placed in a luminometer chamber after the physiological level of shear stress was applied to the HASMC surfaces. The chamber was housed inside a highly sensitive photomultiplier tube. It detected ultraweak photon emission in response to the [Ca2+]i transient. In the presence of 2.0mM extracellular Ca2+, a shear stress of 12dyn∕cm2, applied for 60s to the top surface of the HASMC monolayer, elicited a sharp increase in [Ca2+]i.

Voltage-dependent calcium channel current in isolated gallbladder smooth muscle cells of guinea pig

1993 ◽  
Vol 264 (6) ◽  
pp. G1066-G1076 ◽  
Author(s):  
T. Shimada
Keyword(s):  
Smooth Muscle ◽  
Guinea Pig ◽  
Smooth Muscle Cells ◽  
Time Course ◽  
Reversal Potential ◽  
High Sensitivity ◽  
Muscle Cells ◽  
Patch Clamp Technique ◽  
Decay Component ◽  
Voltage Dependent

The voltage-dependent Ca2+ current was studied in enzymatically dispersed guinea pig gallbladder smooth muscle cells using the whole cell patch-clamp technique. Depolarizing voltage (V) steps induced an inward current (I) that was carried by Ca2+. The threshold potential was -40 to -30 mV, the maximal current was observed at +10 to +20 mV, and the reversal potential was around +80 mV. I-V curves obtained with holding potentials of -80 and -40 mV were not significantly different. This current had a high sensitivity to dihydropyridine drugs, and the Ba2+ or Sr2+ current was larger than the Ca2+ current. Activation was accelerated by increasing the membrane potential. In general, the time course of decay was well fitted by the sum of two exponentials, but consideration of a third (ultra-slow) decay component was also necessary when the current generated by a 2-s command pulse was analyzed. Superimposition of activation and inactivation curves showed the presence of a significant window current. Carbachol suppressed the Ca2+ current only when the pipette contained a low concentration of ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid. These results show that the L-type Ca2+ current is dominant in gallbladder smooth muscle cells and may contribute to excitation-contraction coupling.

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