Stimulation of Ca2+ current by phorbol esters in rat myometrial cells is dependent on intracellular Ca2+ concentration

1996 ◽  
Vol 8 (8) ◽  
pp. 1147 ◽  
Author(s):  
M Kusaka ◽  
N Sperelakis
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Voltage Clamp ◽  
Phorbol Esters ◽  
Cell Voltage ◽  
Muscle Cells ◽  
Whole Cell ◽  
Perforated Patch ◽  
Kinase C ◽  
Whole Cell Voltage Clamp

The effects of phorbol esters on the L-type Ca2+ current (ICa(L)) were investigated using nystatin-perforated patch and standard whole-cell voltage clamp in uterine smooth muscle cells isolated from late-pregnant rats. Using nystatin-perforated patch to maintain the integrity of the cytosol components, phorbol 12-myristate 13-acetate (PMA, 300 nM) increased ICa(L). When the standard whole-cell voltage clamp was used, the effect of PMA was dependent on the Ca2+ concentration in the pipette solution: PMA enhanced ICa(L) at pCa 6 and pCa 7 but not at pCa 10 or pCa 8. The effect of PMA was reversed by a selective inhibitor of protein kinase C, calphostin-C (500 nM). It is concluded that phorbol esters stimulate ICa(L) in uterine muscle cells and that the isoform of protein kinase C involved in this effect is Ca2+ dependent. This mechanism may be involved in the regulation of uterine contraction during pregnancy.

Protein kinase C stimulates Ca2+ current in pregnant rat myometrial cells

1994 ◽  
Vol 72 (11) ◽  
pp. 1304-1307 ◽  
Author(s):  
Keiichi Shimamura ◽  
Masumi Kusaka ◽  
Nicholas Sperelakis
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Voltage Clamp ◽  
Cell Voltage ◽  
Pregnant Rat ◽  
Whole Cell ◽  
Myometrial Cells ◽  
Kinase C ◽  
Whole Cell Voltage Clamp ◽  
Voltage Dependent

The factors that regulate the voltage-dependent Ca2+ channels in pregnant uterine smooth muscle cells have not been elucidated, including any roles for protein kinase C (PKC). Therefore, the role of PKC in the regulation of the slow (L type) Ca2+ channels was examined in myometrial cells isolated from late pregnant (18–19 day) rat uterus, using the nystatin-perforated whole-cell voltage clamp. A PKC activator, phorbol 12, 13-dibutyrate (PDB), increased the L-type Ca2+ current (ICa(L)). Bath application of PDB (0.03 and 0.3 μM) increased the peak amplitude of ICa(L) by 21 ± 14% (n = 6) and 37 ± 8% (n = 9, p < 0.01), respectively. PDB did not change the holding current or shift the current–voltage relationship for ICa(L). The PKC inhibitors, H-7 (20 μM) or staurosporine (10 nM), reversed the effect of PDB. These results indicate that PKC may play a role in regulating Ca2+ channel function in pregnant rat myometrial cells and, therefore, may be involved in control of uterine contraction.Key words: protein kinase C, phorbol ester, calcium current, myometrial cell, nystatin-perforated patch, whole-cell voltage clamp.

Physiological and pharmacological properties of muscle cells isolated from the flatworm Bdelloura candida (Tricladia)

Parasitology ◽  
1994 ◽  
Vol 109 (3) ◽  
pp. 325-335 ◽  
Author(s):  
K. L. Blair ◽  
P. A. V. Anderson
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Voltage Clamp ◽  
Muscle Cells ◽  
Muscle Fibres ◽  
Pharmacological Properties ◽  
Single Muscle ◽  
Kinase C

SummaryA protocol for dissociating single muscle fibres from intact flatworms was developed. Muscle fragments of various sizes were obtained, many with their cell bodies, or myocytons, intact. Many of the fibres were spontaneously contractile, and they and others contracted in response to applications of transmitter candidates, activators of protein kinase C and the anthelmintic praziquantel. The responses were all similar to those evoked in strips of tissue. Voltage clamp recordings from the isolated muscle fibres revealed that they possess an inward Ca2+ current and 3 separate K+ currents. These results indicate that muscle fibres in Bdelloura bear receptors for neurotransmitters and that preparations of dispersed muscle fibres can be used for studying the basic physiological and pharmacological properties of platyhelminth muscle.

Protein kinase C inhibits delayed rectifier K+ current in rabbit vascular smooth muscle cells

1996 ◽  
Vol 271 (1) ◽  
pp. H109-H119 ◽  
Author(s):  
E. A. Aiello ◽  
O. Clement-Chomienne ◽  
D. P. Sontag ◽  
M. P. Walsh ◽  
W. C. Cole
Keyword(s):  
Smooth Muscle ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Vascular Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Outward Current ◽  
Muscle Cells ◽  
Delayed Rectifier ◽  
Whole Cell ◽  
Kinase C

The effect of protein kinase C (PKC) activation on 4-aminopyridine (4-AP)-sensitive delayed rectifier current (IdK) was studied in isolated rabbit portal vein smooth muscle cells by use of standard whole cell voltage clamp. The effects of the phorbol ester, 4 beta-phorbol 12,13-dibutyrate (PdBu, 100 nM) and diacylglycerol analogues, 1,2-dioctanoyl-sn-glycerol (1,2-diC8, 10 microM) and 1,3-dioctanoyl-sn-glycerol (1,3-diC8, 10 microM), on macroscopic whole cell IdK were assessed in myocytes dialyzed with 10 mM 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA) and 5 mM ATP (20-22 degrees C). Activation of PKC by 1,2-diC8 or PdBu caused a decline in IdK that was reversed with washout of drug. 1,2-diC8 had no effect on outward current present after exposure to 4-AP (20 mM). The inactive analogue, 1,3-diC8, did not affect IdK, but subsequent exposure to the active analogue, 1,2-diC8, caused a marked depression of the current. The inhibition of IdK by 1,2-diC8 was significantly reduced by intracellular dialysis with the inhibitors of PKC, chelerythrine (50 microM) and calphostin C (1 microM). Substitution of extracellular Ca2+ with Mg2+ in the presence of 10 mM intracellular BAPTA did not affect the suppression of IdK by 1,2-diC8, indicating the involvement of a Ca(2+)-independent isoform of PKC. This study suggests a novel signal transduction mechanism for inhibition of 4-AP-sensitive IdK involving a phosphotransferase reaction catalyzed by PKC in vascular smooth muscle myocytes.

scholarly journals Role of phospholipase A2 in expression of the scavenger pathway in cultured aortic smooth muscle cells stimulated with phorbol 12-myristate 13-acetate

1994 ◽  
Vol 303 (1) ◽  
pp. 247-253 ◽  
Author(s):  
N Morisaki ◽  
K Yokote ◽  
K Takahashi ◽  
M Otabe ◽  
Y Saito ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Smooth Muscle Cells ◽  
Phospholipase A2 ◽  
Phorbol Esters ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Muscle Cells ◽  
Kinase C

We have demonstrated that cultured intimal smooth muscle cells (SMC) from thickened intima can metabolize acetylated low-density lipoprotein (LDL) by a scavenger pathway, but medial SMC from normal arteries cannot. In this study we investigated the expression mechanism of the scavenger pathway in medial SMC using a phorbol ester. Medial SMC were incubated with 10(-10)-10(-7) M phorbol 12-myristate 13-acetate (PMA) for 1-24 h and then their degradation of 125I-labelled acetylated LDL was assayed. Unstimulated SMC degraded little acetylated LDL, but incubation for 24 h with PMA dose-dependently stimulated its degradation by SMC, the optimal PMA concentration being 1 x 10(-8) M. Induction of expression of the scavenger pathway required more than 4 h of incubation with PMA and was completely inhibited by cycloheximide. In addition expression of the scavenger pathway was not transient but stable. Induction of expression of the scavenger pathway by PMA was not inhibited by protein kinase C inhibitors, but was inhibited about 50% by phospholipase A2 inhibitors. The study, using various phorbol esters, indicated that induction of the scavenger pathway was well correlated with their ability to stimulate phospholipase A2 in medial SMC but not with their ability to activate protein kinase C. Moreover, incubation with exogenous phospholipase A2 (0.1-10 units/ml) or its product, lysophosphatidylcholine (0.01-100 micrograms/ml) dose-dependently increased degradation of 125I-labelled acetylated LDL in medial SMC. Lysophosphatidylcholine was most effective in various lysophospholipids. These results suggest that PMA induced the scavenger pathway in part by stimulating phospholipase A2 in medial SMC, and that a product, lysophosphatidylcholine, is a mediator of expression of the scavenger pathway.

scholarly journals Inhibition of DNA synthesis by phorbol esters through protein kinase C in cultured rabbit aortic smooth muscle cells

FEBS Letters ◽  
1987 ◽  
Vol 217 (1) ◽  
pp. 69-73 ◽  
Author(s):  
Ken-ichi Kariya ◽  
Yasuo Fukumoto ◽  
Terutaka Tsuda ◽  
Yasuhiro Kawahara ◽  
Hisashi Fukuzaki ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Smooth Muscle Cells ◽  
Dna Synthesis ◽  
Phorbol Esters ◽  
Muscle Cells ◽  
Aortic Smooth Muscle ◽  
Kinase C ◽  
Inhibition Of Dna Synthesis
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