Ca2+-activated Cl- current in retinal arteriolar smooth muscle.
OBJECTIVE
To characterize the biophysical, pharmacologic, and functional properties of the Ca(2+)-activated Cl(-) current in retinal arteriolar myocytes.


METHODS
Whole-cell perforated patch-clamp recordings were made from myocytes within intact isolated arteriolar segments. Arteriolar tone was assessed using pressure myography.


RESULTS
Depolarizing of voltage steps to -40 mV and greater activated an L-type Ca(2+) current (I(Ca(L))) that was followed by a sustained current. Large tail currents (I(tail)) were observed on stepping back to -80 mV. The sustained current and I(tail) reversed close to 0 mV in symmetrical Cl(-) concentrations. The ion selectivity sequence for I(tail) was I(-)> Cl(-)> glucuronate. Outward I(tail) was sensitive to the Cl(-) channel blockers 9-anthracene-carboxylic acid (9-AC; 1 mM), 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic acid (SITS; 1 mM), and disodium 4,4'-diisothiocyanatostilbene-2,2'-disulfonate (DIDS; 1 mM), but only DIDS produced a substantial (78%) block of inward tail currents at -100 mV. I(tail) was decreased in magnitude when the normal bathing medium was substituted with Ca(2+)-free solution or if I(Ca(L)) was inhibited by 1 microM nimodipine. Caffeine (10 mM) produced large transient currents that reversed close to the Cl(-) equilibrium potential and were blocked by 1 mM DIDS or 100 microM tetracaine. DIDS had no effect on basal vascular tone in pressurized arterioles but dramatically reduced the level of vasoconstriction observed in the presence of 10 nM endothelin-1.


CONCLUSIONS
Retinal arteriolar myocytes have I(Cl(Ca)), which may be activated by Ca(2+) entry through L-type Ca(2+) channels or Ca(2+) release from intracellular stores. This current appears to contribute to agonist-induced retinal vasoconstriction.
McGahon
Mary K
MK
Centre for Vision and Vascular Sciences, School of Medicine and Dentistry, The Queen's University of Belfast, Institute of Clinical Sciences, The Royal Victoria Hospital, United Kingdom.
Needham
Maurice A
MA
Scholfield
C Norman
CN
McGeown
J Graham
JG
Curtis
Tim M
TM
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000818:Animals; D001160:Arterioles / Q000187:drug effects / Q000502:physiology; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000378:metabolism; D018118:Chloride Channels / Q000502:physiology*; D008297:Male; D008564:Membrane Potentials; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D032389:Myocytes, Smooth Muscle / Q000378:metabolism*; D009213:Myography; D018408:Patch-Clamp Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D012161:Retinal Artery / Q000187:drug effects / Q000502:physiology*; D012519:Sarcoplasmic Reticulum / Q000378:metabolism
D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D018118:Chloride Channels; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D002118:Calcium
Circ Res. 1994 Oct;75(4):742-50
7923619
Am J Physiol Cell Physiol. 2000 Nov;279(5):C1327-35
11029279
Am J Physiol. 1997 May;272(5 Pt 1):L959-68
9176262
J Physiol. 1998 Mar 1;507 ( Pt 2):433-9
9518703
J Physiol. 1991 Apr;435:21-39
1770436
Circ Res. 2007 Mar 16;100(5):703-11
17293477
Br J Pharmacol. 1999 Aug;127(8):1819-31
10482912
Pflugers Arch. 1991 Dec;419(6):553-8
1664933
Invest Ophthalmol Vis Sci. 2000 Jul;41(8):2279-85
10892874
Invest Ophthalmol Vis Sci. 2005 Sep;46(9):3281-7
16123430
J Physiol. 2001 Jul 15;534(Pt. 2):395-408
11454959
Pflugers Arch. 2002 Jan;443(3):473-82
11810219
Br J Pharmacol. 1996 Jun;118(4):1065-71
8799583
Am J Physiol Heart Circ Physiol. 2007 Feb;292(2):H1001-8
17040965
Br J Pharmacol. 1991 Dec;104(4):1000-6
1667281
Am J Physiol. 1992 May;262(5 Pt 2):F799-806
1317119
J Physiol. 1988 Oct;404:557-73
2473199
Am J Physiol Cell Physiol. 2005 Jan;288(1):C122-31
15355851
J Physiol. 1990 Sep;428:501-16
1700110
J Gen Physiol. 1943 Sep 20;27(1):37-60
19873371
Am J Physiol. 1996 Aug;271(2 Pt 1):C435-54
8769982
Am J Hypertens. 1995 Jan;8(1):90-4
7734105
Pflugers Arch. 1996 Oct;432(6):970-9
8781190
Microvasc Res. 2000 Mar;59(2):233-42
10684729
Can J Physiol Pharmacol. 2005 Jul;83(7):541-56
16091780
J Physiol. 1989 Oct;417:241-61
2482883
J Gen Physiol. 1988 Aug;92(2):145-59
2459299
Kidney Int. 1996 Sep;50(3):864-72
8872961
J Gen Physiol. 2000 Jan;115(1):59-80
10613919
Microcirculation. 2007 Jan;14(1):11-24
17365658
J Physiol. 1997 Jul 15;502 ( Pt 2):259-64
9263908
Am J Physiol. 1998 Oct;275(4):C940-50
9755047
J Physiol. 1949 Mar 1;108(1):37-77
18128147
J Physiol. 2003 Jun 1;549(Pt 2):453-69
12665603
Ann R Coll Surg Engl. 1977 Nov;59(6):470-5
931327
Annu Rev Physiol. 2005;67:719-58
15709976
Hypertension. 2000 Jan;35(1 Pt 2):173-8
10642294
Channels (Austin). 2007 May-Jun;1(3):141-3
18690028
J Physiol. 1999 Apr 15;516 ( Pt 2):365-76
10087337