Pyrimidine nucleotides suppress KDR currents and depolarize rat cerebral arteries by activating Rho kinase.
This study examined whether, and by what signaling and ionic mechanisms, pyrimidine nucleotides constrict rat cerebral arteries. Cannulated cerebral arteries stripped of endothelium and pressurized to 15 mmHg constricted in a dose-dependent manner to UTP. This constriction was partly dependent on the depolarization of smooth muscle cells and the activation of voltage-operated Ca(2+) channels. The depolarization and constriction induced by UTP were unaffected by bisindolylmaleimide I, a PKC inhibitor that abolished phorbol ester (PMA)-induced constriction in cerebral arteries. In contrast, the Rhokinase inhibitor Y-27632 attenuated the ability of UTP to both constrict and depolarize cerebral arteries. With patch-clamp electrophysiology, a voltage-dependent delayed rectifying K(+) (K(DR)) current was isolated and shown to consist of a slowly inactivating 4-aminopyridine (4-AP)-sensitive and an -insensitive component. The 4-AP-sensitive K(DR) current was potently suppressed by UTP through a mechanism that was not dependent on PKC. This reflects observations that demonstrated that 1) a PKC activator (PMA) had no effect on K(DR) and 2) PKC inhibitors (calphostin C or bisindolylmaleimide I) could not prevent the suppression of K(DR) by UTP. The Rho kinase inhibitor Y-27632 abolished the ability of UTP to inhibit the K(DR) current, as did inhibition of RhoA with C3 exoenzyme. Cumulatively, these observations indicate that Rho kinase signaling plays an important role in eliciting the cerebral constriction induced by pyrimidine nucleotides. Moreover, they demonstrate for the first time that Rhokinase partly mediates this constriction by altering ion channels that control membrane potential and Ca(2+) influx through voltage-operated Ca(2+) channels.
HM-86, Heritage Medical Research Bldg., Univ. of Calgary, 3330 Hospital Dr. NW, Calgary, Alberta, Canada T2N 4N1.
Kevin D
KD
Luykenaar
Suzanne E
SE
Brett
Bin Nan
BN
Wu
William B
WB
Wiehler
Donald G
DG
Welsh
D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000494:pharmacology; D000577:Amides / Q000494:pharmacology; D000818:Animals; D002536:Cerebral Arteries / Q000187:drug effects* / Q000201:enzymology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D047908:Intracellular Signaling Peptides and Proteins; D008564:Membrane Potentials / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000201:enzymology; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011725:Pyridines / Q000494:pharmacology; D011743:Pyrimidines / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D018048:Receptors, Purinergic P2 / Q000378:metabolism; D014544:Uridine Triphosphate / Q000378:metabolism; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D054460:rho-Associated Kinases
D000577:Amides; D004791:Enzyme Inhibitors; D047908:Intracellular Signaling Peptides and Proteins; D015221:Potassium Channels; D011725:Pyridines; D011743:Pyrimidines; D018048:Receptors, Purinergic P2; D014662:Vasoconstrictor Agents; C108830:Y 27632; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases; D011493:Protein Kinase C; C030986:pyrimidine; D014544:Uridine Triphosphate