Further investigations into the endothelium-dependent hyperpolarizing effects of bradykinin and substance P in porcine coronary artery.
In porcine coronary arteries, smooth muscle hyperpolarizations produced by the nitric oxide donor, NOR-1, and the prostacyclin analogue, iloprost, were compared with those induced by substance P and bradykinin and attributed to the endothelium-derived hyperpolarizing factor (EDHF). In the presence of 300 microM L-nitroarginine and 10 microM indomethacin, iloprost-induced hyperpolarizations were partially inhibited by 10 microM glibenclamide whereas those to NOR-1, substance P and bradykinin were unaffected. Hyperpolarizations produced by maximally-effective concentrations of NOR-1 and NS1619 were identical (to -65 mV). They were significantly less than those generated by either substance P or bradykinin (to approximately -80 mV) and were abolished by iberiotoxin 100 nM, a concentration which had essentially no effect on responses to substance P or bradykinin. Incubation of segments of intact arteries for 16 - 22 h in bicarbonate-buffered Krebs solution had little effect on EDHF responses to substance P or bradykinin. In contrast, after incubation for this period of time in HEPES-buffered Tyrode solution or Krebs containing 10 mM HEPES the EDHF response to substance P was abolished and that to bradykinin was markedly reduced. The residual bradykinin-induced hyperpolarization following incubation in Tyrode solution was inhibited by iberiotoxin and by 10 microM 17-octadecynoic acid. We conclude that substance P activates only the EDHF pathway in the presence of nitric oxide synthase and cyclo-oxygenase inhibitors. Incubation in HEPES-buffered Tyrode solution abolishes the EDHF responses to substance P and bradykinin to reveal an additional hyperpolarizing mechanism, associated with the opening of K(+) channels, activated only by bradykinin.
Edwards
G
G
School of Biological Sciences, University of Manchester, Manchester M13 9PT, UK. gedwards@man.ac.uk
Félétou
M
M
Gardener
M J
MJ
Glen
C D
CD
Richards
G R
GR
Vanhoutte
P M
PM
Weston
A H
AH
D000818:Animals; D001639:Bicarbonates / Q000494:pharmacology; D001685:Biological Factors / Q000502:physiology; D001920:Bradykinin / Q000494:pharmacology*; D002021:Buffers; D003331:Coronary Vessels / Q000187:drug effects* / Q000502:physiology; D019806:Cromakalim / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000502:physiology*; D011464:Epoprostenol / Q000494:pharmacology; D005905:Glyburide / Q000494:pharmacology; D006531:HEPES / Q000494:pharmacology; D066298:In Vitro Techniques; D007213:Indomethacin / Q000494:pharmacology; D007552:Isotonic Solutions / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology; D020030:Nitric Oxide Donors / Q000494:pharmacology; D019335:Nitroarginine / Q000494:pharmacology; D010455:Peptides / Q000494:pharmacology; D012965:Sodium Chloride / Q000494:pharmacology; D013373:Substance P / Q000494:pharmacology*; D013552:Swine; D013997:Time Factors; D014665:Vasodilator Agents / Q000494:pharmacology
D001639:Bicarbonates; D001685:Biological Factors; D002021:Buffers; D007552:Isotonic Solutions; D020030:Nitric Oxide Donors; D010455:Peptides; C037692:Tyrode's solution; D014665:Vasodilator Agents; C067410:endothelium-dependent hyperpolarization factor; D019806:Cromakalim; D019335:Nitroarginine; D013373:Substance P; D012965:Sodium Chloride; C064719:iberiotoxin; D011464:Epoprostenol; D006531:HEPES; D001920:Bradykinin; D005905:Glyburide; D007213:Indomethacin