Effects of renal nerve stimulation on intrarenal blood flow in rats with intact or inactivated NO synthases.
OBJECTIVE
We studied a possible action of nitric oxide (NO), an intrarenal vasodilator, to buffer a decrease in renal perfusion induced by electrical stimulation of renal nerves (RNS).


METHODS
In anaesthetized rats RNS was performed (15 V, 2 ms pulse duration) for 10 s at the frequencies of 2, 3.5, 5 and 7.5 Hz. The total renal blood flow (RBF), an index of cortical perfusion, was measured using a Transonic probe on the renal artery. The outer and inner medullary blood flow (OMBF, IMBF) was measured by laser-Doppler flowmetry. The effect of RNS on RBF, OMBF and IMBF was determined in rats which were either untreated or pre-treated with L-NAME (0.6 or 1.8 mg kg(-1) i.v.), or S-methyl thiocitrulline (SMTC, 20 microg kg(-1) min(-1) i.v.), a selective inhibitor of neuronal NO synthase (nNOS).


RESULTS
In untreated rats, RNS decreased IMBF significantly less than RBF and OMBF. High-dose L-NAME treatment significantly enhanced the RNS induced decrease of RBF but not of OMBF or IMBF. SMTC treatment significantly enhanced the decrease of IMBF, without affecting the response of RBF or OMBF.


CONCLUSIONS
At intact NO synthesis the inner medullary circulation is not controlled by renal nerves to the extent observed for the outer medulla or cortex. NO generated by all NOS isoforms present in the kidney buffers partly the intrarenal vasoconstriction triggered by electrical RNS. The NO derived from nNOS seems of particular importance in the control of inner medullary perfusion, interacting with NO generated by endothelial NOS and renal nerves.
Walkowska
A
A
Laboratory of Renal and Body Fluid Physiology, M. Mossakowski Medical Research Centre, Polish Academy of Sciences, Pawińskiego 5, 02-106 Warsaw, Poland.
Badzyńska
B
B
Kompanowska-Jezierska
E
E
Johns
E J
EJ
Sadowski
J
J
D000818:Animals; D002956:Citrulline / Q000031:analogs & derivatives* / Q000494:pharmacology; D004558:Electric Stimulation / Q000379:methods; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007668:Kidney / Q000187:drug effects / Q000294:innervation / Q000502:physiology*; D007679:Kidney Medulla / Q000502:physiology; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D012079:Renal Circulation / Q000187:drug effects / Q000502:physiology*; D013890:Thiourea / Q000031:analogs & derivatives* / Q000494:pharmacology; D014665:Vasodilator Agents / Q000494:pharmacology
D004791:Enzyme Inhibitors; D014665:Vasodilator Agents; D002956:Citrulline; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D013890:Thiourea; C086717:S-methylthiocitrulline; D019331:NG-Nitroarginine Methyl Ester