Differential effects of endothelin on activation of renal mechanosensory nerves: stimulatory in high-sodium diet and inhibitory in low-sodium diet

2006 ◽  
Vol 291 (5) ◽  
pp. R1545-R1556 ◽  
Author(s):  
Ulla C. Kopp ◽  
Michael Z. Cicha ◽  
Lori A. Smith
Keyword(s):  
Substance P ◽  
Dietary Intake ◽  
Sensory Nerves ◽  
High Sodium ◽  
Sodium Diet ◽  
Low Sodium Diet ◽  
Low Sodium ◽  
Salt Sensitive Hypertension ◽  
High Sodium Diet ◽  
Pelvic Pressure

Activation of renal mechanosensory nerves is enhanced by high and suppressed by low sodium dietary intake. Afferent renal denervation results in salt-sensitive hypertension, suggesting that activation of the afferent renal nerves contributes to water and sodium balance. Another model of salt-sensitive hypertension is the endothelin B receptor (ETBR)-deficient rat. ET and its receptors are present in sensory nerves. Therefore, we examined whether ET receptor blockade altered the responsiveness of the renal sensory nerves. In anesthetized rats fed high-sodium diet, renal pelvic administration of the ETBR antagonist BQ-788 reduced the afferent renal nerve activity (ARNA) response to increasing renal pelvic pressure 7.5 mmHg from 26 ± 3 to 9 ± 3% and the PGE2-mediated renal pelvic release of substance P from 9 ± 1 to 3 ± 1 pg/min. Conversely, in rats fed low-sodium diet, renal pelvic administration of the ETAR antagonist BQ-123 enhanced the ARNA response to increased renal pelvic pressure from 9 ± 2 to 23 ± 6% and the PGE2-mediated renal pelvic release of substance P from 0 ± 0 to 6 ± 1 pg/min. Adding the ETAR antagonist to ETBR-blocked renal pelvises restored the responsiveness of renal sensory nerves in rats fed a high-sodium diet. Adding the ETBR antagonist to ETAR-blocked pelvises suppressed the responsiveness of the renal sensory nerves in rats fed a low-sodium diet. In conclusion, activation of ETBR and ETAR contributes to the enhanced and suppressed responsiveness of renal sensory nerves in conditions of high- and low-sodium dietary intake, respectively. Impaired renorenal reflexes may contribute to the salt-sensitive hypertension in the ETBR-deficient rat.

Endogenous angiotensin modulates PGE2-mediated release of substance P from renal mechanosensory nerve fibers

2002 ◽  
Vol 282 (1) ◽  
pp. R19-R30 ◽  
Author(s):  
Ulla C. Kopp ◽  
Michael Z. Cicha ◽  
Lori A. Smith
Keyword(s):  
Substance P ◽  
Nerve Fibers ◽  
Ang Ii ◽  
High Sodium ◽  
Sodium Diet ◽  
Low Sodium Diet ◽  
Low Sodium ◽  
Pelvic Perfusion ◽  
High Sodium Diet ◽  
Pelvic Pressure

Increasing renal pelvic pressure increases afferent renal nerve activity (ARNA) by a prostaglandin E2(PGE2)-mediated release of substance P (SP) from renal pelvic sensory nerves. We examined whether the ARNA responses were modulated by high- and low-sodium diets. Increasing renal pelvic pressure resulted in greater ARNA responses in rats fed a high-sodium than in those fed a low-sodium diet. In rats fed a low-sodium diet, increasing renal pelvic pressure 2.5 and 7.5 mmHg increased ARNA 2 ± 1 and 13 ± 1% before and 12 ± 1 and 22 ± 2% during renal pelvic perfusion with 0.44 mM losartan. In rats fed a high-sodium diet, similar increases in renal pelvic pressure increased ARNA 10 ± 1 and 23 ± 3% before and 1 ± 1 and 11 ± 2% during pelvic perfusion with 15 nM ANG II. The PGE2-mediated release of SP from renal pelvic nerves in vitro was enhanced in rats fed a high-sodium diet and suppressed in rats fed a low-sodium diet. The PGE2 concentration required for SP release was 0.03, 0.14, and 3.5 μM in rats fed high-, normal-, and low-sodium diets. In rats fed a low-sodium diet, PGE2increased renal pelvic SP release from 5 ± 1 to 6 ± 1 pg/min without and from 12 ± 1 to 21 ± 2 pg/min with losartan in the incubation bath. Losartan had no effect on SP release in rats fed normal- and high-sodium diets. ANG II modulates the responsiveness of renal pelvic mechanosensory nerves by inhibiting PGE2-mediated SP release from renal pelvic nerve fibers.

scholarly journals Dietary sodium modulates the interaction between efferent and afferent renal nerve activity by altering activation of α2-adrenoceptors on renal sensory nerves

2011 ◽  
Vol 300 (2) ◽  
pp. R298-R310 ◽  
Author(s):  
Ulla C. Kopp ◽  
Michael Z. Cicha ◽  
Lori A. Smith ◽  
Saku Ruohonen ◽  
Mika Scheinin ◽  
...  
Keyword(s):  
Substance P ◽  
Sodium Intake ◽  
Sensory Nerves ◽  
Nerve Activity ◽  
Renal Nerve ◽  
High Sodium ◽  
Sodium Diet ◽  
Low Sodium ◽  
Renal Nerve Activity ◽  
High Sodium Diet

Activation of efferent renal sympathetic nerve activity (ERSNA) increases afferent renal nerve activity (ARNA), which then reflexively decreases ERSNA via activation of the renorenal reflexes to maintain low ERSNA. The ERSNA-ARNA interaction is mediated by norepinephrine (NE) that increases and decreases ARNA by activation of renal α1-and α2-adrenoceptors (AR), respectively. The ERSNA-induced increases in ARNA are suppressed during a low-sodium (2,470 ± 770% s) and enhanced during a high-sodium diet (5,670 ± 1,260% s). We examined the role of α2-AR in modulating the responsiveness of renal sensory nerves during low- and high-sodium diets. Immunohistochemical analysis suggested the presence of α2A-AR and α2C-AR subtypes on renal sensory nerves. During the low-sodium diet, renal pelvic administration of the α2-AR antagonist rauwolscine or the AT1 receptor antagonist losartan alone failed to alter the ARNA responses to reflex increases in ERSNA. Likewise, renal pelvic release of substance P produced by 250 pM NE (from 8.0 ± 1.3 to 8.5 ± 1.6 pg/min) was not affected by rauwolscine or losartan alone. However, rauwolscine+losartan enhanced the ARNA responses to reflex increases in ERSNA (4,680 ± 1,240%·s), and renal pelvic release of substance P by 250 pM NE, from 8.3 ± 0.6 to 14.2 ± 0.8 pg/min. During a high-sodium diet, rauwolscine had no effect on the ARNA response to reflex increases in ERSNA or renal pelvic release of substance P produced by NE. Losartan was not examined because of low endogenous ANG II levels in renal pelvic tissue during a high-sodium diet. Increased activation of α2-AR contributes to the reduced interaction between ERSNA and ARNA during low-sodium intake, whereas no/minimal activation of α2-AR contributes to the enhanced ERSNA-ARNA interaction under conditions of high sodium intake.

The Influence of Sodium Intake on the Pressor Response to Angiotensin II in the Unanaesthetized Rat

1976 ◽  
Vol 50 (4) ◽  
pp. 285-291
Author(s):  
Barbara L. Slack ◽  
J. M. Ledingham
Keyword(s):  
Angiotensin Ii ◽  
Dose Response ◽  
Response Curve ◽  
Dose Response Curve ◽  
Response Curves ◽  
High Sodium ◽  
Sodium Diet ◽  
Low Sodium Diet ◽  
Low Sodium ◽  
High Sodium Diet

1. Dose—response curves for the pressor activity of angiotensin II have been determined in unanaesthetized rats receiving diets containing 2·5% (w/w) or 0·007% (w/w) sodium; the different diets were administered in various sequences. 2. In comparison with those from rats receiving a low sodium diet, the dose—response curves were displaced to the left on the high sodium diet, indicating a greater response to angiotensin, and this displacement persisted for a period of approximately 7 days after the diet was changed from high to low sodium. The dose—response curve subsequently shifted to the right when the low sodium diet was maintained for longer. 3. There was a negative correlation between the slope of the dose—response curve and the basal blood pressure in all groups; the correlation was significant in three out of the five different treatment groups. 4. Basal blood pressures were significantly raised in rats on the high sodium diet for 7 days. 5. A number of possible mechanisms have been considered to explain both the parallel shift of the dose—response curve and alteration in its slope. It is concluded that the observed findings are compatible with an action of sodium-loading on the sensitivity of the smooth muscle cell to angiotensin, on the resting of the renin—angiotensin system, on the rate of in-activation of angiotensin and on a change in initial length of the muscle fibre.

Recovery from acute renal failure predisposes hypertension and secondary renal disease in response to elevated sodium

2007 ◽  
Vol 293 (1) ◽  
pp. F269-F278 ◽  
Author(s):  
Kimberly R. Spurgeon-Pechman ◽  
Deborah L. Donohoe ◽  
David L. Mattson ◽  
Hayley Lund ◽  
Leilani James ◽  
...  
Keyword(s):  
Renal Failure ◽  
Acute Renal Failure ◽  
Renal Disease ◽  
Ischemia Reperfusion ◽  
Salt Diet ◽  
High Sodium ◽  
Sodium Diet ◽  
Low Sodium Diet ◽  
Low Sodium ◽  
High Sodium Diet

Recovery of renal function is a well-characterized feature of models of acute renal failure; however, more recent studies have reported a predisposition to chronic renal disease. This study sought to determine the susceptibility to sodium-dependent hypertension following recovery from ischemic acute renal failure. Following ischemia-reperfusion (I/R) injury, rats were allowed to recover for 35 days on a 0.4% salt diet, then were switched to 4.0% salt diet for an additional 28 days. Blood pressure was significantly increased in postischemic rats switched to high-sodium diet at day 35 (19 ± 9 mmHg) compared with postischemic rats maintained on low-sodium diet. Plasma renin activity and creatinine clearance were not affected by I/R injury. The ischemic injury combined with transfer to 4.0% salt diet resulted in marked renal hypertrophy characterized by interstitial cellular deposition, tubular dilation, and enhanced rates of albumin excretion. Glomerular structure was altered in post-I/R rats switched to high-sodium diet but not in those maintained on low-sodium diets. When rats were acclimated to high-sodium diet before I/R injury, the early injury was similar to that observed in animals acclimated to low-sodium diet, and these animals progressed rapidly toward chronic kidney disease, as evidenced by advancement of albuminuria. These data suggest that the recovery from acute I/R injury is not complete, compromises Na homeostasis, and predisposes hypertension and secondary renal disease.

Inappropriate values of the juxtaglomerular index during changes in rat serum sodium levels

1969 ◽  
Vol 47 (2) ◽  
pp. 210-213 ◽  
Author(s):  
L. E. Sutherland
Keyword(s):  
Serum Sodium ◽  
Urinary Sodium ◽  
Dietary Sodium ◽  
Rat Serum ◽  
High Sodium ◽  
Sodium Diet ◽  
Low Sodium Diet ◽  
Low Sodium ◽  
High Sodium Diet

Extreme variations of dietary sodium are reflected in serum and urinary sodium levels. In rats fed a high-sodium diet and then abruptly switched to a low-sodium diet or fed a low-sodium diet and then switched to a high-sodium diet, the juxtaglomerular index was dissociated from both serum and urinary sodium values.

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