title: Potassium-induced intermittent vasomotion in rat isolated pulmonary artery.
abstract: A novel intermittent vasomotion induced by potassium in rat pulmonary artery was investigated with a view to characterize the ion channel mechanisms governing such secondary oscillatory activity. Isometric force was recorded from ring preparations of rat isolated pulmonary arteries incubated in a modified Krebs buffer containing K⁺ 15-18 mM and nitro-L-arginine methyl ester (10 µM). Tissues exhibited a stable pattern of on-off vasomotion consisting of intermittent contractile wave (ICW) activity with a periodicity of 7-8/hr and a rising phase of oscillatory ramping-up of contractile tone at 7 cycles/min. L-channel antagonists arrested (nicardipine; 3 nM) or retarded (verapamil, 30 nM) ICW activity with a concomitant wave asynchronization or decrease in amplitude. Mibefradil (30-100 nM) inhibited ICW ramping-up without affecting ICW period. Niflumic acid (1.0-3.0 µM) exerted dual actions on ICW amplitude but arrested ICW cycling at 10 µM. K⁺-channel blockers produced shortening of ICW period (4-aminopyridine, Ba²⁺ 30 µM; Cs⁺ 3.0-6.0 mM) and increase (tetraethylammonium; 1.0 mM) or decrease (Ba²⁺, 100 µM) in amplitude. Cyclopiazonic acid caused ICW asynchronization (0.3 µM) or cessation (1.0 µM) of ICW cycling. Fasudil retarded ramping-up contractile oscillations without changing ICW period. The inhibitory effects of nicardipine, niflumic acid and cyclopiazonic acid were partially surmounted by small additional increments in [K⁺](e). Our findings support the concept that a secondary vasomotive oscillator operates in rat pulmonary artery which enables the activity of the primary oscillator to be regulated in a cyclic manner via sarcolemmal L-type Ca²⁺ channels and an array of K conductances.
authors.affiliation: Division of BioMedical Sciences, Faculty of Medicine, Memorial University, St. John's, NL, Canada.
authors.forename: Detlef
authors.initials: D
authors.lastname: Bieger
authors.forename: Carol Ann
authors.initials: CA
authors.lastname: Ford
authors.forename: Reza
authors.initials: R
authors.lastname: Tabrizchi
mesh_terms: D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine / Q000031:analogs & derivatives / Q000494:pharmacology; D015761:4-Aminopyridine / Q000494:pharmacology; D000818:Animals; D001464:Barium / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D008297:Male; D020748:Mibefradil / Q000494:pharmacology; D009529:Nicardipine / Q000494:pharmacology; D009544:Niflumic Acid / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology*; D015221:Potassium Channels / Q000187:drug effects* / Q000502:physiology*; D011651:Pulmonary Artery / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D019789:Tetraethylammonium / Q000494:pharmacology; D014700:Verapamil / Q000494:pharmacology
chemical_list: D007211:Indoles; D015221:Potassium Channels; D001464:Barium; D020748:Mibefradil; D009544:Niflumic Acid; D019789:Tetraethylammonium; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D015761:4-Aminopyridine; D014700:Verapamil; D009529:Nicardipine; C049347:fasudil; D011188:Potassium; C000543:cyclopiazonic acid