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Departments of 1 Pediatrics and 2 Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, Texas 75235-9063
The proximal tubule
synthesizes and luminally secretes high levels of angiotensin II, which
modulate proximal tubule transport independently of systemic
angiotensin II. The purpose of this in vivo microperfusion study is to
examine whether the renal nerves modulate the effect of intraluminal
angiotensin II on proximal tubule transport. The decrement in volume
reabsorption after addition of 10
4 M luminal enalaprilat
is a measure of the role of luminal angiotensin II on transport. Acute
denervation decreased volume reabsorption (2.97 ± 0.14 vs.
1.30 ± 0.21 nl · mm
1 · min
1,
P < 0.001). Although luminal 10
4 M
enalaprilat decreased volume reabsorption in controls (2.97 ± 0.14 vs. 1.61 ± 0.26 nl · mm
1 · min
1,
P < 0.001), it did not after acute denervation
(1.30 ± 0.21 vs. 1.55 ± 0.19 nl · mm
1 · min
1). After
chronic denervation, volume reabsorption was unchanged from sham
controls (2.26 ± 0.28 vs. 2.70 ± 0.19 nl · mm
1 · min
1). Addition
of luminal 10
4 M enalaprilat decreased volume
reabsorption in sham control (2.70 ± 0.19 vs. 1.60 ± 0.10 nl · mm
1 · min
1,
P < 0.05) but not with chronic denervation (2.26 ± 0.28 vs. 2.07 ± 0.20 nl · mm
1 · min
1). Addition
of 10
8 M angiotensin II to the lumen does not affect
transport due to the presence of luminal angiotensin II. However,
addition of 10
8 M angiotensin II to the tubular lumen
increased the volume reabsorption after both acute (1.30 ± 0.21 vs. 2.67 ± 0.18 nl · mm
1 · min
1,
P < 0.05) and chronic denervation (2.26 ± 0.28 vs. 3.57 ± 0.44 nl · mm
1 · min
1,
P < 0.01). These data indicate that renal denervation
abolished the luminal enalaprilat-sensitive component of proximal
tubule transport, which is consistent with the renal nerves playing a role in the modulation of the intraluminal angiotensin II mediated component of proximal tubule transport.
volume reabsorption; renal denervation; renin-angiotensin system
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