Identification of [3H]P1075 binding sites and P1075-activated K+ currents in ovine choroid plexus cells.
This study examined the pharmacological characteristics of binding sites for the potent K+ channel opener [3H]P1075, as well as the functional effects of P1075 on ionic currents and membrane potential, in ovine choroid plexus (OCP) cells. [3H]P1075 bound to OCP cells with a Kd of 26 +/- 4 nM and a Bmax of 10400 +/- 480 sites/cell. Labelled sites were stereoselective and inhibited by potassium channel openers with a rank order of potency: P1075 > BMS-182264, ((4-[[9cyanoimino)[(1,2,2-trimethylpropyl)amino]-methyl]amino]benz onitrile) > pinacidil >> nicorandil > diazoxide. The K(ATP) channel antagonist glyburide inhibited [3H]P1075 binding with a Ki of 2 microM. The presence of K(ATP) channels on OCP cells was examined by patch clamp and fluorescent (membrane-potential sensitive dye) techniques. In some cells, P1075 activated an outward potassium current which was blocked by glyburide. P1075 produced a glyburide-sensitive, concentration-dependent, hyperpolarization of OCP cells. Levcromakalim hyperpolarized more strongly than its 3R,4S enantiomer, BRL 38226 ((3R-trans)-3,4-dihydro-3-hydroxy-2,2-dimethyl-4-(2-oxo-1-pyrrolidinyl)- 2H-1-benzopyran-6-carbonitrile) indicating a stereoselective interaction. These data indicate that epithelial OCP cells contain glyburide-sensitive K(ATP) channels.
Dickinson
K E
KE
Bristol-Myers Squibb Pharmaceutical Research Institute, Princeton, NJ 08543-4000, USA.
Baska
R A
RA
Cohen
R B
RB
Bryson
C C
CC
Smith
M A
MA
Schroeder
K
K
Lodge
N J
NJ
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001665:Binding Sites / Q000187:drug effects; D002478:Cells, Cultured; D002831:Choroid Plexus / Q000187:drug effects / Q000378:metabolism*; D004594:Electrophysiology; D006146:Guanidines / Q000494:pharmacology*; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000819:agonists / Q000378:metabolism*; D011725:Pyridines / Q000494:pharmacology*; D012756:Sheep; D014665:Vasodilator Agents / Q000494:pharmacology*
D006146:Guanidines; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D011725:Pyridines; D014665:Vasodilator Agents; C073896:N-cyano-N'-(1,1-dimethylpropyl)-N''-(3-pyridinyl)guanidine; D000255:Adenosine Triphosphate