BACKGROUND: As yet, there are only limited data available on the exact role of endothelin (ET) acting through endothelin-A (ETA) receptors in renal sodium and water regulation and the potential functional implications of an interaction of the renal ET system with renal nerves in normotensive and spontaneously hypertensive rats. METHODS: Experiments were carried out in 64 male conscious spontaneously hypertensive rats and in 56 normotensive Wistar-Kyoto (WKY) rats. Bilateral renal denervation (BRD) was performed in 32 spontaneously hypertensive rats and 28 WKY rats 7 days before the experiments. The ETA receptor antagonist, BQ-123 (16.4 nmol/kg x min intravenously) or the endothelin-B (ETB) receptor antagonist, BQ-788 (25 nmol/kg x min intravenously) were infused at a rate of 25 microL/min for 50 minutes. RESULTS: Renal papillary ET-1 concentration in intact spontaneously hypertensive rats was 67.8% lower than in intact WKY rats (154 +/- 40 fmol/mg protein vs. 478 +/- 62 fmol/mg protein, P < 0.01). BRD decreased papillary ET-1 by 73.5% in WKY rats to 127 +/- 19 fmol/mg protein (P < 0.001), but had no effect in spontaneously hypertensive rats (122 +/- 37 fmol/mg protein). BRD, BQ-123, or BQ-788 did not affect glomerular filtration rate (GFR) or renal blood flow (RBF) in any of the groups. In intact WKY, BQ-123 decreased urine flow rate (V) from 4.65 +/- 0.44 microL/min.100 g body weight to 2.44 +/- 0.35 microL/min.100 g body weight (P < 0.01), urinary excretion of sodium (UNaV) from 238.2 +/- 27.4 to 100.2 +/- 17.0 (P < 0.01) and potassium (UKV) from 532.1 +/- 62.6 nmol/min.100 g body weight to 243.0 +/- 34.2 nmol/min.100 g body weight (P < 0.001), whereas BQ-788 decreased only V and UNaV. In renal denervated WKY, BQ-123 or BQ-788 did not alter V, UNaV, or UKV. In intact spontaneously hypertensive rats BQ-123 but not BQ-788 decreased V from 3.94 +/- 0.48 microL/min.100 g body weight to 2.55 +/- 0.44 microL/min.100 g body weight (P < 0.05). In renal denervated spontaneously hypertensive rats neither BQ-123 nor BQ-788 affected V, UNaV, or UKV. CONCLUSION: An interaction between ET and renal nerves is involved in the control of renal function. Moreover, renal nerves participate in the regulation of ET-1 production within the kidney. Finally, decreased synthesis of ET-1 in the renal papilla of spontaneously hypertensive rats may contribute to development and/or maintenance of hypertension due to modulation of renal excretory function.
BACKGROUND: As yet, there are only limited data available on the exact role of endothelin (ET) acting through endothelin-A (ETA) receptors in renal sodium and water regulation and the potential functional implications of an interaction of the renal ET system with renal nerves in normotensive and spontaneously hypertensiverats. METHODS: Experiments were carried out in 64 male conscious spontaneously hypertensiverats and in 56 normotensive Wistar-Kyoto (WKY) rats. Bilateral renal denervation (BRD) was performed in 32 spontaneously hypertensiverats and 28 WKY rats 7 days before the experiments. The ETA receptor antagonist, BQ-123 (16.4 nmol/kg x min intravenously) or the endothelin-B (ETB) receptor antagonist, BQ-788 (25 nmol/kg x min intravenously) were infused at a rate of 25 microL/min for 50 minutes. RESULTS: Renal papillary ET-1 concentration in intact spontaneously hypertensiverats was 67.8% lower than in intact WKY rats (154 +/- 40 fmol/mg protein vs. 478 +/- 62 fmol/mg protein, P < 0.01). BRD decreased papillary ET-1 by 73.5% in WKY rats to 127 +/- 19 fmol/mg protein (P < 0.001), but had no effect in spontaneously hypertensiverats (122 +/- 37 fmol/mg protein). BRD, BQ-123, or BQ-788 did not affect glomerular filtration rate (GFR) or renal blood flow (RBF) in any of the groups. In intact WKY, BQ-123 decreased urine flow rate (V) from 4.65 +/- 0.44 microL/min.100 g body weight to 2.44 +/- 0.35 microL/min.100 g body weight (P < 0.01), urinary excretion of sodium (UNaV) from 238.2 +/- 27.4 to 100.2 +/- 17.0 (P < 0.01) and potassium (UKV) from 532.1 +/- 62.6 nmol/min.100 g body weight to 243.0 +/- 34.2 nmol/min.100 g body weight (P < 0.001), whereas BQ-788 decreased only V and UNaV. In renal denervated WKY, BQ-123 or BQ-788 did not alter V, UNaV, or UKV. In intact spontaneously hypertensiveratsBQ-123 but not BQ-788 decreased V from 3.94 +/- 0.48 microL/min.100 g body weight to 2.55 +/- 0.44 microL/min.100 g body weight (P < 0.05). In renal denervated spontaneously hypertensiverats neither BQ-123 nor BQ-788 affected V, UNaV, or UKV. CONCLUSION: An interaction between ET and renal nerves is involved in the control of renal function. Moreover, renal nerves participate in the regulation of ET-1 production within the kidney. Finally, decreased synthesis of ET-1 in the renal papilla of spontaneously hypertensiverats may contribute to development and/or maintenance of hypertension due to modulation of renal excretory function.
Authors: Lauren G Douma; G Ryan Crislip; Kit-Yan Cheng; Dominique Barral; Sarah Masten; Meaghan Holzworth; Emilio Roig; Krystal Glasford; Kevin Beguiristain; Wendy Li; Phillip Bratanatawira; I Jeanette Lynch; Brian D Cain; Charles S Wingo; Michelle L Gumz Journal: Can J Physiol Pharmacol Date: 2020-09-11 Impact factor: 2.273
Authors: Bryan K Becker; Amanda C Feagans; Daian Chen; Malgorzata Kasztan; Chunhua Jin; Joshua S Speed; Jennifer S Pollock; David M Pollock Journal: Am J Physiol Regul Integr Comp Physiol Date: 2017-07-12 Impact factor: 3.619