The role of nitric oxide in the regulation of glomerular haemodynamics in humans.
BACKGROUND
According to experimental data, the afferent glomerular arteriole is particularly under control of nitric oxide (NO). By use of pharmacological manoeuvres, we examined whether this finding holds true in the human renal circulation in vivo.


METHODS
Seventy-seven volunteers (aged 50+/-9 years) with mild to moderate essential hypertension (n = 57) or arterial normotension (n = 20) were examined. Basal NO activity in the renal circulation was assessed by the change of renal plasma flow (RPF) through systemic infusion of the NO synthase inhibitor, N(G)-monomethyl-L-arginine (L-NMMA; 4.25 mg/kg). Hypertensive patients were treated over 8 weeks with either the calcium-channel blocker amlodipine or the AT(1)-receptor blocker valsartan, primarily dilating the afferent and efferent arteriole, respectively. Subsequently, renal haemodynamics and NO activity in the renal circulation were determined again.


RESULTS
L-NMMA reduced RPF in normotensive (by 57+/-70 ml/min/1.73 m(2); P<0.01) and hypertensive subjects (by 46+/-56 ml/min/1.73 m(2); P<0.001) with no significant difference between the two groups. The decrease of RPF through L-NMMA was closely related with the glomerular filtration rate (GFR; r = 0.39, P<0.001). Administration of amlodipine increased GFR by 7.1+/-12.1 ml/min/1.73 m(2); (P<0.01) and in parallel reduced the response of RPF to L-NMMA to 19+/-48 ml/min/1.73 m(2); (P<0.05). In contrast, valsartan maintained GFR and left the response of RPF to L-NMMA unchanged.


CONCLUSIONS
NO plays an important role in the regulation of human glomerular haemodynamics, probably with a greater contribution to afferent than to efferent arteriolar tone in man.
Department of Medicine IV/4, University of Erlangen-Nuremburg, Erlangen, Germany.
Christian
C
Delles
Arnfried U
AU
Klingbeil
Markus P
MP
Schneider
Renate
R
Handrock
Tim
T
Schäufele
Roland E
RE
Schmieder
D000328:Adult; D017311:Amlodipine / Q000494:pharmacology; D057911:Angiotensin Receptor Antagonists; D002121:Calcium Channel Blockers / Q000494:pharmacology; D005919:Glomerular Filtration Rate / Q000502:physiology; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D007678:Kidney Glomerulus / Q000502:physiology*; D008875:Middle Aged; D009569:Nitric Oxide / Q000502:physiology*; D013777:Tetrazoles / Q000494:pharmacology; D014633:Valine / Q000031:analogs & derivatives / Q000494:pharmacology; D000068756:Valsartan; D014665:Vasodilator Agents / Q000494:pharmacology
D057911:Angiotensin Receptor Antagonists; D002121:Calcium Channel Blockers; D013777:Tetrazoles; D014665:Vasodilator Agents; D017311:Amlodipine; D009569:Nitric Oxide; D000068756:Valsartan; D014633:Valine