Purinoreceptor-mediated current in myocytes from renal resistance arteries.
OBJECTIVE
Ionotropic purinoreceptors (P2X) in renal vascular smooth muscle cells (RVSMCs) are involved in mediating the sympathetic control and paracrine regulation of renal blood flow (RBF). Activation of P2X receptors elevates [Ca(2+)](i) in RVSMCs triggering their contraction, leading to renal vasoconstriction and decrease of RBF. The goal of the present work was to characterize the P2X receptor-mediated ionic current (I(P2X)) and to identify the types of P2X receptors expressed in myocytes isolated from interlobar and arcuate arteries of rat kidney.


METHODS
The expression of P2X receptors in isolated RVSMCs was analysed by reverse transcription (RT)-PCR. I(P2X) and membrane potential were recorded using the amphotericin B-perforated patch method.


RESULTS
RT-PCR analysis on single RVSMCs showed the presence of genes encoding P2X1 and P2X4 receptors. Under voltage clamp conditions, the selective P2X receptor agonist alphabeta-methylene ATP (alphabeta-meATP) evoked I(P2X) similar to that induced by ATP. Under current clamp conditions, both ATP and alphabeta-meATP evoked a spike-like membrane depolarization followed by a sustained depolarization, linking P2X receptors in RVSMCs to sympathetic control of renal vascular tone. A selective antagonist of P2X1 receptors, NF279, reduced I(P2X) amplitude by approximately 65% concentration-dependently manner within the nanomolar to sub-micromolar range. The residual current was resistant to micromolar concentrations of NF279, but was inhibited by sub-millimolar to millimolar concentrations of NF279.


CONCLUSIONS
Two types of functional P2X receptors, monomeric P2X1 and heteromeric P2X1/4 receptors, are expressed in RVSMCs. Our study has identified important targets for possible pharmacological intervention in the sympathetic control of renal circulation.
Harhun
Maksym I
MI
Ion Channels and Cell Signalling Centre, Division of Basic Medical Sciences, St. George's University of London, London, UK. m.harhun@sgul.ac.uk
Povstyan
Oleksandr V
OV
Gordienko
Dmitri V
DV
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001158:Arteries / Q000187:drug effects / Q000502:physiology*; D007668:Kidney / Q000098:blood supply*; D007700:Kinetics; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D042282:Microdissection; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism; D009928:Organ Specificity; D009994:Osmolar Concentration; D018408:Patch-Clamp Techniques; D058910:Purinergic P2 Receptor Agonists; D058919:Purinergic P2 Receptor Antagonists; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011921:Rats, Inbred WKY; D018048:Receptors, Purinergic P2 / Q000235:genetics / Q000378:metabolism*; D058469:Receptors, Purinergic P2X; D058848:Receptors, Purinergic P2X4; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013498:Suramin / Q000031:analogs & derivatives / Q000494:pharmacology
C114657:NF 279; C548228:P2rx4 protein, rat; D058910:Purinergic P2 Receptor Agonists; D058919:Purinergic P2 Receptor Antagonists; D012333:RNA, Messenger; D018048:Receptors, Purinergic P2; D058469:Receptors, Purinergic P2X; D058848:Receptors, Purinergic P2X4; D013498:Suramin; D000255:Adenosine Triphosphate; C002630:alpha,beta-methyleneadenosine 5'-triphosphate