Effects of acute and chronic unilateral renal denervation on the tubuloglomerular feedback mechanism.
We recently observed a time-dependent resetting of the tubuloglomerular feedback (TGF) sensitivity to a subnormal level after acute unilateral renal denervation (aDNX). The present investigation compares the effects of aDNX with those of chronic unilateral renal denervation (cDNX), i.e one week after aDNX. All experiments were performed in anaesthetized rats prepared for micropuncture. cDNX led to increases in urine, sodium and potassium excretion in denervated kidneys, while contralateral kidneys showed reduced excretion of these parameters. GFR was increased in denervated kidneys, but unchanged on the contralateral side. TGF activity was determined by measuring the maximal stop-flow pressure response (delta Psf) and the tubular flow rate at which 50% of the maximal response occurred (turning point; TP). cDNX decreased TGF sensitivity, as indicated by an increased TP from 19.1 nL/min in sham-DNX to 26.1 nL/min. Concomitantly, TP in contralateral kidneys was significantly decreased to 15.9 nL/min, aDNX led to a greater sensitivity reduction: TP increased from 19.8 to 34.0 nL/min and contralaterally TP decreased to 14.0 nL/min. delta Psf in cDNX increased by 63% compared to sham-DNX, while on the contralateral side this was unchanged. No difference in delta Psf was found between control, DNX and contralateral kidneys in the aDNX group. In summary, these experiments show that the previously reported decrease in TGF sensitivity in aDNX kidneys still persists after one week, although less pronounced. As a result of the decreased TGF sensitivity, GFR is kept on a high level in cDNX kidneys. Contralateral kidneys show reversed resetting.
Thorup
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C
Department of Physiology & Biophysics, Lund University, Sweden.
Kurkus
J
J
Ollerstam
A
A
Persson
A E
AE
D000818:Animals; D003714:Denervation; D004573:Electrolytes / Q000652:urine; D005246:Feedback / Q000502:physiology; D005919:Glomerular Filtration Rate / Q000502:physiology; D007668:Kidney / Q000294:innervation / Q000502:physiology*; D007678:Kidney Glomerulus / Q000502:physiology*; D007684:Kidney Tubules / Q000502:physiology*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D012079:Renal Circulation / Q000502:physiology; D014563:Urodynamics / Q000502:physiology
D004573:Electrolytes