Lack of contribution of P2X receptors to neurally mediated vasoconstriction in the rabbit kidney in vivo.
OBJECTIVE
The contribution of adenosine triphosphate (ATP) to the neural control of regional renal perfusion in vivo remains unknown. We therefore examined whether P2X receptors mediate renal vascular responses to electrical stimulation of the renal nerves (RNS) in pentobarbitone anaesthetized rabbits.


METHODS
Responses to RNS were tested before and during renal arterial infusion of alpha,beta-methylene ATP (alpha,beta-mATP, 7-56 microg kg(-1) min(-1)) to desensitize P2X1 receptors. RNS consisted of 3 min trains at graded frequencies and short trains of RNS (4-32 pulses).


RESULTS
Three-minute trains of RNS reduced renal blood flow (RBF), cortical laser Doppler flux (CLDF), and medullary LDF (MLDF) by -90 +/- 3%, -89 +/- 3% and -31 +/- 11%, respectively, at 4 Hz. MLDF was reduced less than CLDF or RBF. During short train RNS, RBF, CLDF and MLDF were reduced by -22 +/- 2%, -15 +/- 2% and -12 +/- 2%, respectively, for 32 s at 1 Hz. CLDF and MLDF were reduced to a similar extent. Infusion of alpha,beta-mATP induced transient reductions in RBF, CLDF and MLDF, but within 5 min these variables had recovered to control levels. Vascular responses to RNS were not significantly altered by alpha,beta-mATP treatment.


CONCLUSIONS
In the rabbit kidney in vivo, alpha,beta-mATP-sensitive receptors mediate vasoconstriction and reduce perfusion in both cortical and medullary vascular beds. However, these receptors do not mediate neurally induced reductions in renal perfusion.
Department of Physiology, Monash University, Melbourne, Vic., Australia. gabriela.eppel@med.monash.edu.au
G A
GA
Eppel
S
S
Ventura
K M
KM
Denton
R G
RG
Evans
D000818:Animals; D004558:Electric Stimulation / Q000379:methods; D006439:Hemodynamics / Q000502:physiology; D007668:Kidney / Q000294:innervation*; D007672:Kidney Cortex / Q000098:blood supply; D007679:Kidney Medulla / Q000098:blood supply; D008297:Male; D011817:Rabbits; D018048:Receptors, Purinergic P2 / Q000502:physiology*; D058469:Receptors, Purinergic P2X; D012079:Renal Circulation / Q000502:physiology*; D013564:Sympathetic Nervous System / Q000502:physiology; D014661:Vasoconstriction / Q000502:physiology*
D018048:Receptors, Purinergic P2; D058469:Receptors, Purinergic P2X