L-S-nitrosothiols: endothelium-derived hyperpolarizing factors in porcine coronary arteries?
OBJECTIVE
Bradykinin-induced, endothelium-derived hyperpolarizing factor (EDHF)-mediated responses depend on Ca-dependent K-channels (KCa) of small (SKCa) and intermediate (IKCa) conductance, inwardly rectifying K (KIR) channels and/or Na-K-ATPase. Here we investigated in porcine coronary arteries (PCAs) whether S-nitrosothiols can act as EDHF.


METHODS
Preconstricted PCAs were exposed to bradykinin, the NO donor S-nitroso-N-penicillamine (SNAP), or the S-nitrosothiols L-S-nitrosocysteine (L-SNC), D-SNC and L-S-nitrosoglutathione (L-SNG), with or without KCl, the NO scavenger hydroxocobalamin, the S-nitrosothiol-depleting agent p-hydroxymercurobenzoic acid (PHMBA) and/or inhibitors of NO synthase (L-NAME), guanylyl cyclase (ODQ), SKCa channels (apamin), KCa channels of large conductance (BKCa) (iberiotoxin), IKCa + BKCa channels (charybdotoxin), KIR channels (BaCl2) or Na-K-ATPase (ouabain).


RESULTS
All agonists concentration-dependently relaxed PCAs. L-NAME, charybdotoxin + apamin, KCl, and ouabain shifted the bradykinin concentration-response curve (CRC) approximately 10-fold to the right. BaCl2 did not exert additional effects on top of ouabain. Full blockade of bradykinin was obtained when combining L-NAME with charybdotoxin + apamin, KCl or ouabain + BaCl2. PHMBA reduced the maximum effect of bradykinin. Iberiotoxin + apamin, alone or on top of L-NAME, did not affect bradykinin, SNAP or L-SNC. ODQ and hydroxocobalamin shifted the SNAP, L-SNC, D-SNC, and L-SNG CRCs approximately 10-fold to the right, and, in combination, fully blocked SNAP-induced effects. Charybdotoxin + apamin shifted the L-SNC and L-SNG CRCs, but not the D-SNC or SNAP CRCs, approximately 5-fold to the right. KCl and ouabain (but not BaCl2) shifted the SNAP, L-SNC and L-SNG CRCs 5-10 fold to the right.


CONCLUSIONS
L-S-nitrosothiols activate SKCa + IKCa channels in a stereoselective manner, whereas NO activates Na-K-ATPase. Since S-nitrosothiols decompose to NO, stored L-S-nitrosothiols may mediate bradykinin-induced, EDHF-dependent relaxation.
Batenburg
Wendy W
WW
Department of Pharmacology, Erasmus MC, Rotterdam, The Netherlands.
de Vries
René
R
Saxena
Pramod R
PR
Danser
A H Jan
AH
D000818:Animals; D001158:Arteries / Q000187:drug effects / Q000502:physiology; D001685:Biological Factors / Q000502:physiology*; D001920:Bradykinin / Q000008:administration & dosage / Q000037:antagonists & inhibitors / Q000494:pharmacology; D003331:Coronary Vessels / Q000187:drug effects* / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D004594:Electrophysiology; D066298:In Vitro Techniques; D009569:Nitric Oxide / Q000502:physiology; D009603:Nitroso Compounds / Q000494:pharmacology*; D011189:Potassium Chloride / Q000494:pharmacology; D013438:Sulfhydryl Compounds / Q000494:pharmacology*; D013552:Swine; D014664:Vasodilation / Q000502:physiology
D001685:Biological Factors; D004338:Drug Combinations; D009603:Nitroso Compounds; D013438:Sulfhydryl Compounds; C067410:endothelium-dependent hyperpolarization factor; D009569:Nitric Oxide; D011189:Potassium Chloride; D001920:Bradykinin