Differential regulation of Na+ transporters along nephron during ANG II-dependent hypertension: distal stimulation counteracted by proximal inhibition

During angiotensin II (ANG II)-dependent hypertension, ANG II stimulates, while hypertension inhibits, Na+ transporter activity to balance Na+ output to input. This study tests the hypothesis that ANG II infusion activates Na+ transporters in the distal nephron while inhibiting transporters along the proximal nephron. Male Sprague-Dawley rats were infused with ANG II (400 ng·kg−1·min−1) or vehicle for 2 wk. Kidneys were dissected (cortex vs. medulla) or fixed for immunohistochemistry (IHC). ANG II increased mean arterial pressure by 40 mmHg, urine Na+ by 1.67-fold, and urine volume by 3-fold, evidence for hypertension and pressure natriuresis. Na+ transporters' abundance and activation [assessed by phosphorylation (-P) or proteolytic cleavage] were measured by immunoblot. During ANG II infusion Na+/H+ exchanger 3 (NHE3) abundance decreased in both cortex and medulla; Na-K-2Cl cotransporter 2 (NKCC2) decreased in medullary thick ascending loop of Henle (TALH) and increased, along with NKCC2-P, in cortical TALH; Na-Cl cotransporter (NCC) and NCC-P increased in the distal convoluted tubule; and epithelial Na+ channel subunits and their cleaved forms were increased in both cortex and medulla. Like NKCC2, STE20/SPS1-related proline alanine-rich kinase (SPAK) and SPAK-P were decreased in medulla and increased in cortex. By IHC, during ANG II NHE3 remained localized to proximal tubule microvilli at lower abundance, and the differential regulation of NKCC2 and NKCC2-P in cortex versus medulla was evident. In summary, ANG II infusion increases Na+ transporter abundance and activation from cortical TALH to medullary collecting duct while the hypertension drives a natriuresis response evident as decreased Na+ transporter abundance and activation from proximal tubule through medullary TALH.

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Abstract 114: K+ Rich Diet During Angiotensin II Hypertension Reduces Renal Na-Cl Cotransporter and Phosphorylation, but Not Blood Pressure

Hypertension ◽

10.1161/hyp.66.suppl_1.114 ◽

2015 ◽

Vol 66 (suppl_1) ◽

Author(s):

Luciana C Veiras ◽

Jiyang Han ◽

Donna L Ralph ◽

Alicia A McDonough

Keyword(s):

Blood Pressure ◽

Urine Volume ◽

Weight Ratio ◽

Distal Tubule ◽

Reduce Blood Pressure ◽

Ang Ii ◽

Sprague Dawley ◽

Sprague Dawley Rats ◽

K Secretion ◽

Pressure Natriuresis

During Ang II hypertension distal tubule Na-Cl Cotransporter (NCC) abundance and its activating phosphorylation (NCCp), as well as Epithelial Na+ channels (ENaC) abundance and activating cleavage are increased 1.5-3 fold. Fasting plasma [K+] is significantly lower in Ang II hypertension (3.3 ± 0.1 mM) versus controls (4.0 ± 0.1 mM), likely secondary to ENaC stimulation driving K+ secretion. The aim of this study was to test the hypothesis that doubling dietary K+ intake during Ang II infusion will lower NCC and NCCp abundance to increase Na+ delivery to ENaC to drive K+ excretion and reduce blood pressure. Methods: Male Sprague Dawley rats (225-250 g; n= 7-9/group) were treated over 2 weeks: 1) Control 1% K diet fed (C1K); 2) Ang II infused (400 ng/kg/min) 1% K diet fed (A1K); or 3) Ang II infused 2% K diet fed (A2K). Blood pressure (BP) was determined by tail cuff, electrolytes by flame photometry and transporters’ abundance by immunoblot of cortical homogenates. Results: As previously reported, Ang II infusion increased systolic BP (from 132 ± 5 to 197 ± 4 mmHg), urine volume (UV, 2.4 fold), urine Na+ (UNaV, 1.3 fold), heart /body weight ratio (1.23 fold) and clearance of endogenous Li+ (CLi, measures fluid volume leaving the proximal tubule, from 0.26 ± 0.02 to 0.51 ± 0.01 ml/min/kg) all evidence for pressure natriuresis. A2K rats exhibited normal plasma [K+] (4.6 ± 0.1 mM, unfasted), doubled urine K+ (UKV, from 0.20 to 0.44 mmol/hr), and increased CLi (to 0.8 ± 0.1 ml/min/kg) but UV, UNaV, cardiac hypertrophy and BP were unchanged versus the A1K group. As expected, NCC, NCCpS71 and NCCpT53 abundance increased in the A1K group to 1.5 ± 0.1, 2.9 ± 0.5 and 2.8 ± 0.4 fold versus C1K, respectively. As predicted by our hypothesis, when dietary K+ was doubled (A2K), Ang II infusion did not activate NCC, NCCpS71 nor NCCpT53 (0.91 ± 0.04, 1.3 ± 0.1 and 1.6 ± 0.2 fold versus C1K, respectively). ENaC subunit abundance and cleavage increased 1.5 to 3 fold in both A1K and A2K groups; ROMK was unaffected by Ang II or dietary K. In conclusion, evidence is presented that stimulation of NCC during Ang II hypertension is secondary to K+ deficiency driven by ENaC stimulation since doubling dietary K+ prevents the activation. The results also indicate that elevation in BP is independent of NCC activation

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Increased AQP2 targeting in primary cultured IMCD cells in response to angiotensin II through AT1 receptor

AJP Renal Physiology ◽

10.1152/ajprenal.00090.2006 ◽

2007 ◽

Vol 292 (1) ◽

pp. F340-F350 ◽

Cited By ~ 78

Author(s):

Yu-Jung Lee ◽

In-Kyung Song ◽

Kyung-Jin Jang ◽

Jakob Nielsen ◽

Jørgen Frøkiær ◽

...

Keyword(s):

Plasma Membrane ◽

Angiotensin Ii ◽

Collecting Duct ◽

Receptor Activation ◽

Ang Ii ◽

Sprague Dawley ◽

Water Reabsorption ◽

Sprague Dawley Rats ◽

Medullary Collecting Duct ◽

Camp Levels

Vasopressin and angiotensin II (ANG II) play a major role in renal water and Na+ reabsorption. We previously demonstrated that ANG II AT1 receptor blockade decreases dDAVP-induced water reabsorption and AQP2 levels in rats, suggesting cross talk between these two peptide hormones ( Am J Physiol Renal Physiol 288: F673–F684, 2005). To directly address this issue, primary cultured inner medullary collecting duct (IMCD) cells from male Sprague-Dawley rats were treated for 15 min with 1) vehicle, 2) ANG II, 3) ANG II + the AT1 receptor blocker candesartan, 4) dDAVP, 5) ANG II + dDAVP, or 6) ANG II + dDAVP + candesartan. Immunofluorescence microscopy revealed that 10−8 M ANG II or 10−11 M dDAVP ( protocol 1) was associated with increased AQP2 labeling of the plasma membrane and decreased cytoplasmic labeling, respectively. cAMP levels increased significantly in response to 10−8 M ANG II and were potentiated by cotreatment with 10−11 M dDAVP. Consistent with this finding, immunoblotting revealed that this cotreatment significantly increased expression of phosphorylated AQP2. ANG II-induced AQP2 targeting was blocked by 10−5 M candesartan. In protocol 2, treatment with a lower concentration of dDAVP (10−12 M) or ANG II (10−9 M) did not change subcellular AQP2 distribution, whereas 10−12 M dDAVP + 10−9 M ANG II enhanced AQP2 targeting. This effect was inhibited by cotreatment with 10−5 M candesartan. ANG II-induced cAMP accumulation and AQP2 targeting were inhibited by inhibition of PKC activity. In conclusion, ANG II plays a role in the regulation of AQP2 targeting to the plasma membrane in IMCD cells through AT1 receptor activation and potentiates the effect of dDAVP on AQP2 plasma membrane targeting.

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Proximal tubule microvilli remodeling and albuminuria in the Ren2 transgenic rat

AJP Renal Physiology ◽

10.1152/ajprenal.00252.2006 ◽

2007 ◽

Vol 292 (2) ◽

pp. F861-F867 ◽

Cited By ~ 17

Author(s):

Melvin R. Hayden ◽

Nazif A. Chowdhury ◽

Shawna A. Cooper ◽

Adam Whaley-Connell ◽

Javad Habibi ◽

...

Keyword(s):

Oxidative Stress ◽

Blood Pressure ◽

Systolic Blood Pressure ◽

Proximal Tubule ◽

Structural Damage ◽

Kidney Tissue ◽

Proximal Tubule Cell ◽

Ang Ii ◽

Sprague Dawley ◽

Sprague Dawley Rats

TG(mRen2)27 (Ren2) transgenic rats overexpress the mouse renin gene, with subsequent elevated tissue ANG II, hypertension, and nephropathy. The proximal tubule cell (PTC) is responsible for the reabsorption of 5–8 g of glomerular filtered albumin each day. Excess filtered albumin may contribute to PTC damage and tubulointerstitial disease. This investigation examined the role of ANG II-induced oxidative stress in PTC structural remodeling: whether such changes could be modified with in vivo treatment with ANG type 1 receptor (AT1R) blockade (valsartan) or SOD/catalase mimetic (tempol). Male Ren2 (6–7 wk old) and age-matched Sprague-Dawley rats were treated with valsartan (30 mg/kg), tempol (1 mmol/l), or placebo for 3 wk. Systolic blood pressure, albuminuria, N-acetyl-β-d-glucosaminidase, and kidney tissue malondialdehyde (MDA) were measured, and ×60,000 transmission electron microscopy images were used to assess PTC microvilli structure. There were significant differences in systolic blood pressure, albuminuria, lipid peroxidation (MDA and nitrotyrosine staining), and PTC structure in Ren2 vs. Sprague-Dawley rats (each P < 0.05). Increased mean diameter of PTC microvilli in the placebo-treated Ren2 rats ( P < 0.05) correlated strongly with albuminuria ( r2 = 0.83) and moderately with MDA ( r2 = 0.49), and there was an increase in the ratio of abnormal forms of microvilli in placebo-treated Ren2 rats compared with Sprague-Dawley control rats ( P < 0.05). AT1R blockade, but not tempol treatment, abrogated albuminuria and N-acetyl-β-d-glucosaminidase; both therapies corrected abnormalities in oxidative stress and PTC microvilli remodeling. These data indicate that PTC structural damage in the Ren2 rat is related to the oxidative stress response to ANG II and/or albuminuria.

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Abstract 41: Fructose Stimulates Na/H Exchanger 3 Activity and Enhances the Ability of Angiotensin II to Activate Na/H Exchanger 3 in the Proximal Tubule

Hypertension ◽

10.1161/hyp.62.suppl_1.a41 ◽

2013 ◽

Vol 62 (suppl_1) ◽

Author(s):

Pablo Cabral ◽

Nancy Hong ◽

Jeffrey Garvin

Keyword(s):

Angiotensin Ii ◽

Proximal Tubule ◽

Physiological Saline ◽

Ang Ii ◽

Sprague Dawley ◽

Basal Rate ◽

Low Concentrations ◽

Sprague Dawley Rats ◽

High Fructose ◽

Salt Sensitive Hypertension

Consumption of high-fructose corn syrup as a sweetener has increased dramatically. Fructose has been implicated in the epidemic of diabetes, obesity and hypertension including salt-sensitive hypertension. However, the mechanisms are poorly understood. The proximal nephron reabsorbs 60-70% of the fluid and Na, and most of the filtered bicarbonate via Na/H exchanger 3. Enhanced proximal nephron transport has been implicated in several forms of hypertension. We hypothesized that fructose stimulates NHE3 activity and enhances the ability of angiotensin II (ANG II) to activate NHE3 in the proximal tubule. To test our hypothesis we isolated and perfused proximal tubules from Sprague Dawley rats. NHE3 activity was measured as the recovery of intracellular pH after an NH4Cl acid pulse using the pH sensitive dye BCECF. The rate of pH recovery was measured in Fluorescent Units per second (FU/sec). In the presence of a 5.5 mM glucose-containing physiological saline the basal rate of pH recovery was 3.1 ± 0.8 FU/sec. When the luminal solution was exchanged to a 0.6 mM glucose + 5 mM fructose-containing physiological saline in a second period, the rate of pH recovery increased to 5 ± 1 FU/sec (p<0.03, n=8).To study whether this effect was due to the addition of fructose or the removal of glucose to the lumen, we performed a separate set of experiments where 5 mM glucose was substituted for 5 mM fructose. In the presence of 0.6 mM glucose the basal rate of pH recovery was 3.6 ± 1.5 FU/sec. When 5 mM fructose was added the rate of pH recovery increased to 5.9 ± 2 FU/sec (p<0.02, n=5). Control experiments showed no differences between periods when 5 mm glucose was added back to the luminal perfusate. Finally, we tested the effect of low concentrations of ANG II in the presence or absence of luminal fructose. In the presence of 5.5 mM glucose, ANG II 10-12 M did not affect the rate of pH recovery (change: -1.1 ± 0.5 FU/sec, n=9). However, in the presence of 5 mM fructose, ANG II increased the rate of pH recovery (change: 4.0 ± 2.2 FU/sec, p< 0.03 n=6). We conclude that acute treatment with fructose stimulates NHE3 activity and enhances the ability of ANG II to activate NHE3 in the proximal tubule. These results may partially explain the mechanism by which a fructose diet induces hypertension.

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Abstract 600: Intrarenal Ghrelin Receptor Antagonism Inhibits cAMP Mediated Angiotensin II Sodium Reabsorption in Normal Rats

Hypertension ◽

10.1161/hyp.62.suppl_1.a600 ◽

2013 ◽

Vol 62 (suppl_1) ◽

Author(s):

Brandon A Kemp ◽

Nancy L Howell ◽

Shetal H Padia

Keyword(s):

Angiotensin Ii ◽

Collecting Duct ◽

Sodium Reabsorption ◽

Ang Ii ◽

Sprague Dawley ◽

Ghrelin Receptor ◽

Sprague Dawley Rats ◽

Ghrelin Receptors ◽

Messenger System

An interaction between angiotensin II (Ang II) and ghrelin has been established in many tissues relevant to cardiovascular control, but nothing is known about their relationship within the kidney. Intrarenal ghrelin receptors (GRs) localize to the collecting duct (CD) where they couple to an adenylyl cyclase second messenger system to increase cAMP and ENaC-dependent Na+ reabsorption. Ang II also stimulates the activity of ENaC in the CD (independent of aldosterone), via actions at AT1Rs. The following studies seek to determine whether CD GRs are an important mechanism of Ang II-induced antinatriuresis. Uninephrectomized Sprague-Dawley rats received 3 cumulative 1h renal interstitial (RI) infusions of vehicle 5% dextrose in water (D5W, N=8), Ang II (2 ng/kg/min, N=8), Ang II + D-LYS-GHRP-6, a highly selective GR antagonist (D-LYS, 2, 4, 6 μg/min, N=8) or D-LYS alone (N=8). Urine Na+ excretion rate (UNaV) was measured each hour and compared to baseline, during which only vehicle was infused. RI fluid was collected each hour for cAMP determinations. RI Ang II induced a significant antinatriuresis (UNaV was reduced by 34% at 1h, P<0.01; by 46% at 2h, P<0.001; and by 56% at 3h, P<0.001 from baseline). Ang II-induced antinatriuresis was accompanied by a significant increase in RI cAMP levels from a baseline value of 2.97±0.56 pmol/mL to 10.9±2.2, 13.4±2.2, and 15.3±2.7 pmol/mL after 1h, 2h, and 3h respectively (all P<0.01). However, each of these effects of RI Ang II infusion was abolished by concurrent GR blockade with D-LYS. These data suggest that intact intrarenal GR activity is necessary for Ang II-induced Na+ reabsorption in vivo. Furthermore, since cAMP fails to increase in response to Ang II when GRs are blocked, (and GRs are known to signal via cAMP in the kidney), these data strongly suggest that one of the mechanisms of Ang II-induced Na+ reabsorption in the kidney is via GR-induced increases in cAMP.

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Vasopressin resistance in potassium depletion: role of Na-K pump

AJP Renal Physiology ◽

10.1152/ajprenal.1992.263.4.f705 ◽

1992 ◽

Vol 263 (4) ◽

pp. F705-F710 ◽

Cited By ~ 2

Author(s):

S. K. Mujais ◽

Y. Chen ◽

N. A. Nora

Keyword(s):

Collecting Duct ◽

Cortical Collecting Duct ◽

Sprague Dawley ◽

Sprague Dawley Rats ◽

Pump Activity ◽

Before And After ◽

Directional Change ◽

Medullary Collecting Duct ◽

Low K ◽

K Depletion

Resistance to the hydrosmotic effects of vasopressin has been described in K depletion. It is not clear whether other effects of vasopressin, notably its effects on the Na-K pump in the collecting duct, are similarly affected. Adrenalectomized male Sprague-Dawley rats were allocated to either a normal K (NK) or low-K (LK) diet. Na-K pump activity (pmol.mm-1.h-1) in cortical collecting duct (CCD) and medullary collecting duct (MCD) was determined at 21 days after allocation to the dietary groups before and after exogenous vasopressin (0.1 U twice daily for 3 days). In animals on NK diet, vasopressin (AVP) led to a doubling of Na-K pump activity in the CCD from 502 +/- 47 to 1,144 +/- 41 pmol.mm-1.h-1 (P < 0.01). In K-depleted animals, which had a higher baseline Na-K pump activity, an increase was also observed from 1,056 +/- 97 to 1,239 +/- 65 pmol.mm-1.h-1 (P < 0.05), but this increase was quantitatively less, with the change being 183 vs. 642 pmol.mm-1.h-1 in K-replete rats. The findings in the MCD were similar; in rats on a NK diet, AVP led to a significant increase in Na-K pump activity from 498 +/- 29 to 830 +/- 28 pmol.mm-1.h-1 (P < 0.01). With K depletion, this directional change was preserved, increasing from 1,380 +/- 49 to 1,556 +/- 45 pmol.mm-1.h-1 (P < 0.05), but was quantitatively less than in K-replete rats, the change being 176 vs. 332 pmol.mm-1.h-1.(ABSTRACT TRUNCATED AT 250 WORDS)

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Effects of ET-1 on water and chloride transport in cortical collecting ducts of the rat

AJP Renal Physiology ◽

10.1152/ajprenal.1993.264.4.f690 ◽

1993 ◽

Vol 264 (4) ◽

pp. F690-F696 ◽

Cited By ~ 25

Author(s):

K. Tomita ◽

H. Nonoguchi ◽

Y. Terada ◽

F. Marumo

Keyword(s):

Water Permeability ◽

Continuous Flow ◽

Chloride Transport ◽

Collecting Duct ◽

Sprague Dawley ◽

Sprague Dawley Rats ◽

Osmotic Water ◽

Collecting Ducts ◽

Medullary Collecting Duct

Endothelin-1 (ET-1) is known as a vasoconstrictor peptide. However, recent reports suggested the effects on the transport of renal tubule. We previously reported that ET-1 inhibited arginine vasopressin (AVP)-dependent adenosine 3',5'-cyclic monophosphate in rat collecting ducts. Physiologically, ET-1 reversibly and significantly inhibited AVP-stimulated water permeability in inner medullary collecting duct (IMCD). We therefore investigated the effects on water and electrolyte transport in rat cortical collecting ducts (CCD), where Na and Cl are actively reabsorbed more than in IMCD. Pathogen-free male Sprague-Dawley rats weighing 80-120 g were used after treatment with deoxycorticosterone pivalate for 1-2 wk. Isolated CCD were microperfused in vitro. The Cl concentration was measured by a continuous-flow ultra-microcolorimeter, and the raffinose concentration was measured as a volume marker by a continuous-flow ultra-microfluorometer. In the presence of 10(-9) M AVP, 10(-8) M ET-1 significantly inhibited fluid absorption (nl.mm-1 x min-1) from 0.25 +/- 0.02 to 0.15 +/- 0.05 (mean +/- SE, n = 6, P < 0.01), Cl absorption (pmol.mm-1 x min-1) from 30. 6 +/- 2.8 to 14.9 +/- 4.0 (P < 0.01), and potential difference (mV) from -5.4 +/- 1.3 to -4.0 +/- 1.2 (P < 0.01). Similar results were obtained in the lower concentration of 10(-10) M AVP and 10(-10) M ET-1. As for the osmotic water permeability (microns/s), 10(-8) M ET-1 significantly inhibited this from 320.1 +/- 50.9 to 202.1 +/- 42.2 (n = 7, P < 0.01) in the presence of 10(-9) M AVP.(ABSTRACT TRUNCATED AT 250 WORDS)

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Acid phosphatase activity in the mammalian nephron

AJP Renal Physiology ◽

10.1152/ajprenal.1984.247.2.f252 ◽

1984 ◽

Vol 247 (2) ◽

pp. F252-F259 ◽

Cited By ~ 1

Author(s):

C. J. Olbricht ◽

L. C. Garg ◽

J. K. Cannon ◽

C. C. Tisher

Keyword(s):

Acid Phosphatase ◽

Proximal Tubule ◽

Collecting Duct ◽

Rabbit Kidney ◽

Male Rat ◽

Thick Ascending Limb ◽

Cortical Collecting Duct ◽

Distal Nephron ◽

S3 Segment ◽

Medullary Collecting Duct

Lysosomal acid phosphatase (AcPase) activity was measured in individual segments of rat and rabbit nephrons employing 4-methylumbelliferyl phosphate as the substrate. Generation of reaction product was linear with incubation time up to 127 min and with tubule length. Activity was much higher in glomeruli and proximal tubules of rat than rabbit kidney. In both rat and rabbit there were higher activities in juxtamedullary than in superficial glomeruli. In rats, AcPase activity decreased from S1 to S3 segments, which parallels the known decrease in the number of lysosomes. Surprisingly, in rabbits of both sexes AcPase activity in the cortical collecting duct (CCD), which contains a limited number of lysosomes, was comparable to levels measured in the S1 and S2 segments of the proximal tubule. Similarly, in the male rat values for AcPase activity in the cortical thick ascending limb, distal convoluted tubule, CCD, and medullary collecting duct paralleled those in the S3 segment. These findings suggest that a considerable amount of AcPase in the distal nephron is either extralysosomal or that the amount of lysosomal AcPase activity per unit volume is greater in distal nephron segments compared with the proximal tubule. Different K'm values for AcPase in S1 segments and CCD were found in the rabbit, suggesting the presence of different isoenzymes.

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Acute calcineurin inhibition with tacrolimus increases phosphorylated UT-A1

AJP Renal Physiology ◽

10.1152/ajprenal.00358.2011 ◽

2012 ◽

Vol 302 (8) ◽

pp. F998-F1004 ◽

Cited By ~ 9

Author(s):

Titilayo O. Ilori ◽

Yanhua Wang ◽

Mitsi A. Blount ◽

Christopher F. Martin ◽

Jeff M. Sands ◽

...

Keyword(s):

Membrane Trafficking ◽

Apical Membrane ◽

Collecting Duct ◽

Membrane Association ◽

Sprague Dawley ◽

Sprague Dawley Rats ◽

Collecting Ducts ◽

Concentrate Urine ◽

Medullary Collecting Duct

UT-A1, the urea transporter present in the apical membrane of the inner medullary collecting duct, is crucial to the kidney's ability to concentrate urine. Phosphorylation of UT-A1 on serines 486 and 499 is important for plasma membrane trafficking. The effect of calcineurin on dephosphorylation of UT-A1 was investigated. Inner medullary collecting ducts from Sprague-Dawley rats were metabolically labeled and treated with tacrolimus to inhibit calcineurin or calyculin to inhibit protein phosphatases 1 and 2A. UT-A1 was immunoprecipitated, electrophoresed, blotted, and total UT-A1 phosphorylation was assessed by autoradiography. Total UT-A1 was determined by Western blotting. A phospho-specific antibody to pser486-UT-A1 was used to determine whether serine 486 can be hyperphosphorylated by inhibiting phosphatases. Inhibition of calcineurin showed an increase in phosphorylation per unit protein at serine 486. In contrast, inhibition of phosphatases 1 and 2A resulted in an increase in UT-A1 phosphorylation but no increase in pser486-UT-A1. In vitro perfusion of inner medullary collecting ducts showed tacrolimus-stimulated urea permeability consistent with stimulated urea transport. The location of phosphorylated UT-A1 in rats treated acutely and chronically with tacrolimus was determined using immunohistochemistry. Inner medullary collecting ducts of the acutely treated rats showed increased apical membrane association of phosphorylated UT-A1 while chronic treatment reduced membrane association of phosphorylated UT-A1. We conclude that UT-A1 may be dephosphorylated by multiple phosphatases and that the PKA-phosphorylated serine 486 is dephosphorylated by calcineurin. This is the first documentation of the role of phosphatases and the specific site of phosphorylation of UT-A1, in response to tacrolimus.

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Abstract P040: Pressure Natriuresis In Female Sprague Dawley Rats: Characteristics And Mechanisms

Hypertension ◽

10.1161/hyp.76.suppl_1.p040 ◽

2020 ◽

Vol 76 (Suppl_1) ◽

Author(s):

Brandon E McFarlin ◽

Donna L Ralph ◽

Alicia A McDonough

Keyword(s):

Blood Pressure ◽

Mean Arterial Pressure ◽

Carotid Artery ◽

Urine Volume ◽

Volume Flow ◽

Lithium Clearance ◽

Sprague Dawley ◽

Electrolyte Excretion ◽

Sprague Dawley Rats ◽

Pressure Natriuresis

Raising blood pressure stimulates pressure natriuresis (P-Nat). In males (M) Sprague Dawley rats (SDR), Na + reabsorption (T Na ) is acutely reduced by retraction of proximal tubule (PT) NHE3 to microvillar base and NaPi2 internalization. In females (F), at baseline PT NHE3 is already at microvillar base and NaPi2 is less abundant than in M. We AIM to determine characteristics and mechanisms of P-Nat in F (vs M) rats. Methods: Inactin anesthetized F and M SDR (n=5/group) were provoked by vasoconstriction (or sham). Mean arterial pressure (MAP) was recorded via carotid artery, urine collected via bladder, Na + transporters’ abundance assessed via immunoblot and localization by immunohistochemistry. Results (Fig 1A): Baseline MAP (mmHg) was lower in F vs. M (91 ± 5 vs.105 ± 3, P =0.04) while urine volume (UV) and electrolyte excretion (UNaV, UKV) were similar. After celiac and mesenteric bed constriction, MAP rose to 128 ± 3 mmHg in both sexes; UNaV, UV and C Na increased 12 to 15-fold in F (all P <0.01) vs 6-fold in M ( P >0.08). Constriction of abdominal aorta further raised UNaV in F with less impact in M. Na + transporters . In F, NHE3 remained at PT microvillar base and NaPi2 was internalized with vasoconstriction. NHE3P (indicating inactivation) abundance increased 29% in F, P =0.058. Lithium clearance, measure of volume flow leaving early nephron, increased 9-fold in F ( P =0.02) vs. 5-fold in M ( P =0.07). F mTAL NHE3, NKCC2p, and SPAKp (co-transporter kinase) abundances were 22, 24, and 43% lower vs shams ( ANOVA P <0.0001). Summary: F vs M SDR exhibit more robust P-Nat associated with less T Na in early nephron and reductions in PT-mTAL Na + transporters, consistent with higher UNaV at any given BP (Fig 1B).

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