Hypotonic swelling stimulates L-type Ca2+ channel activity in vascular smooth muscle cells through PKC

2004 ◽  
Vol 287 (2) ◽  
pp. C413-C421 ◽  
Author(s):  
Yanfeng Ding ◽  
Dean Schwartz ◽  
Philip Posner ◽  
Juming Zhong
Keyword(s):  
Smooth Muscle ◽  
Protein Kinase ◽  
Portal Vein ◽  
Smooth Muscle Cells ◽  
Muscle Cells ◽  
Cell Swelling ◽  
Hypotonic Solution ◽  
Channel Activity ◽  
Rabbit Portal Vein ◽  
Hypotonic Swelling

It has been suggested that L-type Ca2+ channels play an important role in cell swelling-induced vasoconstriction. However, there is no direct evidence that Ca2+ channels in vascular smooth muscle are modulated by cell swelling. We tested the hypothesis that L-type Ca2+ channels in rabbit portal vein myocytes are modulated by hypotonic cell swelling via protein kinase activation. Ba2+ currents ( IBa) through L-type Ca2+ channels were recorded in smooth muscle cells freshly isolated from rabbit portal vein with the conventional whole cell patch-clamp technique. Superfusion of cells with hypotonic solution reversibly enhanced Ca2+ channel activity but did not alter the voltage-dependent characteristics of Ca2+ channels. Bath application of selective inhibitors of protein kinase C (PKC), Ro-31–8425 or Go-6983, prevented IBa enhancement by hypotonic swelling, whereas the specific protein kinase A (PKA) inhibitor KT-5720 had no effect. Bath application of phorbol 12,13-dibutyrate (PDBu) significantly increased IBa under isotonic conditions and prevented current stimulation by hypotonic swelling. However, PDBu did not have any effect on IBa when cells were first exposed to hypotonic solution. Furthermore, downregulation of endogenous PKC by overnight treatment of cells with PDBu prevented current enhancement by hypotonic swelling. These data suggest that hypotonic cell swelling can enhance Ca2+ channel activity in rabbit portal vein smooth muscle cells through activation of PKC.

Properties of a Cl−current activated by cell swelling in rabbit portal vein vascular smooth muscle cells

1998 ◽  
Vol 275 (5) ◽  
pp. H1524-H1532 ◽  
Author(s):  
I. A. Greenwood ◽  
W. A. Large
Keyword(s):  
Smooth Muscle ◽  
Portal Vein ◽  
Smooth Muscle Cells ◽  
Physiological Role ◽  
External Solution ◽  
Muscle Cells ◽  
Cell Swelling ◽  
Equilibrium Potential ◽  
Dependent Manner ◽  
Rabbit Portal Vein

In rabbit portal vein smooth muscle cells, application of a hypotonic external solution caused cell swelling and evoked an outwardly rectifying Cl− current. The hypotonicity-activated current was markedly reduced by the anti-estrogen tamoxifen (10 μM) and was inhibited by DIDS in a voltage-dependent manner [the concentration required to inhibit the current by 50% (IC50) at −50 and +100 mV was 21 and 5 μM DIDS, respectively]. Indanyloxyacetic acid 94 (IAA-94) and niflumic acid also inhibited the hypotonicity-activated current, with 50% inhibition produced at concentrations of ∼200 and 100 μM, respectively. In isotonic conditions, application of tamoxifen and DIDS to cells decreased the holding current due to the inhibition of a resting conductance that was outwardly rectifying and reversed at the Cl− equilibrium potential. These data show that rabbit portal vein myocytes have a resting Cl− conductance that is enhanced by cell swelling; its possible physiological role is discussed.

β-Adrenoceptor activation and PKA regulate delayed rectifier K+ channels of vascular smooth muscle cells

1998 ◽  
Vol 275 (2) ◽  
pp. H448-H459 ◽  
Author(s):  
E. Alejandro Aiello ◽  
A. Todd Malcolm ◽  
Michael P. Walsh ◽  
William C. Cole
Keyword(s):  
Signal Transduction ◽  
Smooth Muscle ◽  
Portal Vein ◽  
Vascular Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Vascular Smooth Muscle Cells ◽  
Muscle Cells ◽  
Catalytic Subunit ◽  
Delayed Rectifier ◽  
Rabbit Portal Vein

Macroscopic 4-aminopyridine (4-AP)-sensitive, delayed rectifier K+ current of vascular smooth muscle cells is increased during β-adrenoceptor activation with isoproterenol via a signal transduction pathway involving adenylyl cyclase and cAMP-dependent protein kinase (PKA) (Aiello, E. A., M. P. Walsh, and W. C. Cole. Am. J. Physiol. 268 ( Heart Circ. Physiol. 37): H926–H934, 1995.). In this study, we identified the single delayed rectifier K+(KDR) channel(s) of rabbit portal vein myocytes affected by treatment with isoproterenol or the catalytic subunit of PKA. 4-AP-sensitive KDR channels of 15.3 ± 0.6 pS ( n = 5) and 14.8 ± 0.6 pS ( n = 5) conductance, respectively, were observed in inside-out (I-O) and cell-attached (C-A) membrane patches in symmetrical KCl recording conditions. The kinetics of activation (time constant of 10.7 ± 3.02 ms) and inactivation (fast and slow time constants of 0.3 and 2.5 s, respectively) of ensemble currents produced by these channels mimicked those reported for inactivating, 4-AP-sensitive whole cell KDR current of vascular myocytes. Under control conditions, the open probability ( NP o) of KDR channels of C-A membrane patches at −40 mV was 0.014 ± 0.005 ( n = 8). Treatment with 1 μM isoproterenol caused a significant, approximately threefold increase in NP o to 0.041 ± 0.02 ( P < 0.05). KDR channels of I-O patches exhibited rundown after ∼5 min, which was not affected by ATP (5 mM) in the bath solution. Treatment with the purified catalytic subunit of PKA (50 nM; 5 mM ATP) restored KDRchannel activity and caused NP o to increase from 0.011 ± 0.003 to 0.138 ± 0.03 ( P < 0.05; n = 11). These data indicate that small-conductance, 15-pS KDRchannels are responsible for inactivating the macroscopic delayed rectifier K+ current of rabbit portal vein myocytes and that the activity of these channels is enhanced by a signal transduction mechanism involving β-adrenoceptors and phosphorylation by PKA at a membrane potential consistent with that observed in the myocytes in situ.

A target K+ channel for the LP-805-induced hyperpolarization in smooth muscle cells of the rabbit portal vein

1993 ◽  
Vol 347 (3) ◽  
pp. 329-335 ◽  
Author(s):  
Masahiro Kamouchi ◽  
Shunichi Kajioka ◽  
Takeshi Sakai ◽  
Kenji Kitamura ◽  
Hirosi Kuriyama
Keyword(s):  
Smooth Muscle ◽  
Portal Vein ◽  
Smooth Muscle Cells ◽  
Muscle Cells ◽  
K Channel ◽  
Rabbit Portal Vein
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