Effects of connexin-mimetic peptides on nitric oxide synthase- and cyclooxygenase-independent renal vasodilation.
BACKGROUND
Research on the physiological role of endothelium-derived hyperpolarizing factor (EDHF) is hampered by the persistent controversy on its nature and mechanisms of action, as well as by the lack of specific inhibitors that are suitable for in vivo use. Recent in vitro studies support a role for gap junctions in EDHF-mediated signal transmission. The present study examines the contribution of gap junctional communication to the EDHF-mediated responses in the rat renal microcirculation in vivo and addresses the physiological role of EDHF.


METHODS
The effects of intrarenal administration of connexin-mimetic peptides on the L-NAME- and indomethacin-resistant renal blood flow (RBF) response to acetylcholine, on basal RBF and on systemic blood pressure were examined.


RESULTS
43Gap 27, a peptide homologous to the second extracellular loop of connexin 43, partially inhibited the L-NAME- and indomethacin-resistant RBF response to acetylcholine, whereas 40Gap 27, homologous to the second extracellular loop of connexin 40, abolished the response. A control peptide, with a replacement of two amino acids in the motif SRPTEK present in the second extracellular loop of connexins 40 and 43, was without effect. None of the peptides affected the response to DETA-NONOate, pinacidil or papaverine. Intrarenal infusion of 43Gap 27 or 40Gap 27 decreased basal RBF and increased mean arterial blood pressure, both in the presence and absence of systemic infusion of L-NAME and indomethacin.


CONCLUSIONS
Inhibition of gap junctional communication with connexin-mimetic peptides blocks EDHF-mediated signal transmission in vivo, as suggested by the abolishment of L-NAME- and indomethacin-resistant renal vasodilation. The peptides also decrease basal RBF and increase blood pressure, supporting a role for tonic EDHF release in the control of tissue perfusion and vascular resistance.
De Vriese
An S
AS
Renal Unit and the Department of Physiology, University Hospital, Gent, Belgium. an.devriese@rug.ac.be
Van de Voorde
Johan
J
Lameire
Norbert H
NH
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001685:Biological Factors / Q000037:antagonists & inhibitors / Q000378:metabolism; D001794:Blood Pressure / Q000502:physiology; D017630:Connexins / Q000737:chemistry / Q000378:metabolism*; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D017629:Gap Junctions / Q000378:metabolism; D006339:Heart Rate / Q000502:physiology; D006977:Hypertension, Renal / Q000378:metabolism; D007213:Indomethacin / Q000494:pharmacology; D008833:Microcirculation / Q000502:physiology; D018716:Molecular Mimicry; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D020030:Nitric Oxide Donors / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D009603:Nitroso Compounds / Q000494:pharmacology; D010446:Peptide Fragments / Q000494:pharmacology*; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012079:Renal Circulation / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology; D014664:Vasodilation / Q000502:physiology*; D014665:Vasodilator Agents / Q000494:pharmacology
D001685:Biological Factors; D017630:Connexins; D016861:Cyclooxygenase Inhibitors; D004791:Enzyme Inhibitors; D020030:Nitric Oxide Donors; D009603:Nitroso Compounds; D010446:Peptide Fragments; D014665:Vasodilator Agents; C067410:endothelium-dependent hyperpolarization factor; C094210:2,2'-(hydroxynitrosohydrazono)bis-ethanamine; D019001:Nitric Oxide Synthase; D011451:Prostaglandin-Endoperoxide Synthases; D000109:Acetylcholine; D019331:NG-Nitroarginine Methyl Ester; D007213:Indomethacin