Differential effects of pulsatile versus steady flow on coronary endothelial membrane potential.
Steady shear stress stimulates transient hyperpolarization coupled to calcium-sensitive potassium (KCa) channels and sustained depolarization linked to chloride-selective channels. Physiological flow is pulsatile not static, and whereas in vivo data suggest phasic shear stress may preferentially activate KCa channels, its differential effects on both currents remain largely unknown. To determine this interaction, coronary endothelial cells were cultured in glass capillary flow tubes, loaded with the voltage-sensitive dye bis-(1,3-dibutylbarbituric acid)trimethine oxonol, and exposed to constant or pulsatile shear stress. The latter was generated by a custom servoperfusion system employing physiological pressure and flow waveforms. Steady shear induced a sustained depolarization inhibited by the Cl- channel blocker DIDS. Even after exposure to steady flow, subsequent transition to pulsatile shear stress further stimulated DIDS-sensitive depolarization. DIDS pretreatment "unmasked" a pulsatile flow-induced hyperpolarization of which magnitude was further enhanced by nifedipine, which augments epoxygenase synthesis. Pulse-shear hyperpolarization was fully blocked by KCa channel inhibition (charybdotoxin + apamin), although these agents had no influence on membrane potential altered by steady flow. Thus KCa-dependent hyperpolarization is preferentially stimulated by pulsatile over steady flow, whereas both can stimulate Cl--dependent depolarization. This supports studies showing greater potency of pulsatile flow for triggering KCa-dependent vasorelaxation.
Qiu
Wei-Ping
WP
Department of Medicine, Johns Hopkins Hospital, Baltimore, MD 21287, USA.
Hu
Qinghua
Q
Paolocci
Nazareno
N
Ziegelstein
Roy C
RC
Kass
David A
DA
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000818:Animals; D001463:Barbiturates / Q000494:pharmacology; D001562:Benzimidazoles / Q000494:pharmacology; D001685:Biological Factors / Q000502:physiology; D001920:Bradykinin / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002417:Cattle; D018118:Chloride Channels / Q000187:drug effects / Q000502:physiology; D003326:Coronary Circulation / Q000502:physiology*; D003331:Coronary Vessels / Q000502:physiology*; D004594:Electrophysiology; D004730:Endothelium, Vascular / Q000166:cytology / Q000502:physiology*; D007555:Isoxazoles / Q000494:pharmacology; D008564:Membrane Potentials / Q000502:physiology; D009543:Nifedipine / Q000494:pharmacology; D024681:Potassium Channels, Calcium-Activated / Q000502:physiology; D013314:Stress, Mechanical
D001463:Barbiturates; D001562:Benzimidazoles; D001685:Biological Factors; D002121:Calcium Channel Blockers; D018118:Chloride Channels; D007555:Isoxazoles; D024681:Potassium Channels, Calcium-Activated; C067410:endothelium-dependent hyperpolarization factor; C052795:bis(1,3-dibutylbarbiturate)trimethine oxonol; C086491:NS 1619; D009543:Nifedipine; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D001920:Bradykinin