Abstract 16993: Sex Differences in Renal Transporter Profile Indicate Lower Proximal Reabsorption in Females

Circulation ◽  
2015 ◽  
Vol 132 (suppl_3) ◽  
Author(s):  
Luciana C Veiras ◽  
An Tran ◽  
Donna L Ralph ◽  
Adriana Castello Costa Girardi ◽  
Alicia A McDonough
Keyword(s):  
Distal Tubule ◽  
Sprague Dawley ◽  
Volume Load ◽  
Sprague Dawley Rats ◽  
Lower Blood ◽  
Functional Consequences ◽  
Blood Pressures ◽  
Renal Transporter ◽  
Pressure Natriuresis ◽  
Quantitative Immunoblotting

Females have lower blood pressure than males before menopause, blunted hypertensive response to AngII, and a leftward shift in pressure natriuresis. Estrogen decreases renal ACE and AT1R and increases NO and AT2R. At the renal transporter level, distal tubule Na+-Cl- cotransporter (NCC) is upregulated by estrogen and more abundant in females, while the loop of Henle (LH) Na+-K+-2Cl- cotransporter (NKCC2) is less abundant. This study aimed to compare female to male apical Na+ transporters’ abundance, distribution, phosphorylation and cleavage and to determine the functional consequences of the differences. Sprague Dawley rats were fasted overnight then fed a 0%KCl meal before termination. The figure displays relative abundance of total and modified (P -phosphorylated, CL-cleaved, FL-full length) transporters expressed along the nephron in females versus males (defined as 1.0), determined by quantitative immunoblotting. Lower abundance of NaPi2, villin, myosin VI, together with higher NHE3-P (inactivation marker) suggest less proximal tubule (PT) reabsorption in females. Confocal immunohistochemistry confirmed that NHE3 localized to the base of the PT microvilli in females (not males) and endogenous CLi+, a marker of volume leaving the PT, was twice as high in females than males. While LH NKCC2 and its regulatory kinase SPAK were not significantly different, distal NCC, and activated NCC-P were more abundant in females, although thiazide sensitive natriuresis was not greater. ENaC α and γ subunits were more activated (-CL) in females. A saline challenge (7% of b.w. saline, i.p.) demonstrated that females excreted a saline load more rapidly than males. Taken together, these results suggest that lower proximal transporters and reabsorption provoke a volume load dependent elevation in NCC and ENaC. This profile in females likely facilitates pressure natriuresis and maintains lower blood pressures.

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

Hypertension ◽  
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

scholarly journals Effects of K+-deficient diets with and without NaCl supplementation on Na+, K+, and H2O transporters' abundance along the nephron

2012 ◽  
Vol 303 (1) ◽  
pp. F92-F104 ◽  
Author(s):  
Mien T. X. Nguyen ◽  
Li E. Yang ◽  
Nicholas K. Fletcher ◽  
Donna H. Lee ◽  
Hetal Kocinsky ◽  
...  
Keyword(s):  
Urine Volume ◽  
Urine Osmolality ◽  
Pool Size ◽  
Sprague Dawley ◽  
Size Regulation ◽  
Aquaporin 2 ◽  
Sprague Dawley Rats ◽  
Lower Blood ◽  
Autosomal Recessive Hypercholesterolemia ◽  
Quantitative Immunoblotting

Dietary potassium (K+) restriction and hypokalemia have been reported to change the abundance of most renal Na+ and K+ transporters and aquaporin-2 isoform, but results have not been consistent. The aim of this study was to reexamine Na+, K+ and H2O transporters' pool size regulation in response to removing K+ from a diet containing 0.74% NaCl, as well as from a diet containing 2% NaCl (as found in American diets) to blunt reducing total diet electrolytes. Sprague-Dawley rats ( n = 5–6) were fed for 6 days with one of these diets: 2% KCl, 0.74% NaCl (2K1Na, control chow) compared with 0.03% KCl, 0.74% NaCl (0K1Na); or 2% KCl, 2%NaCl (2K2Na) compared with 0.03% KCl, 2% NaCl (0K2Na, Na+ replete). In both 0K1Na and 0K2Na there were significant decreases in: 1) plasma [K+] (<2.5 mM); 2) urinary K+ excretion (<5% of control); 3) urine osmolality and plasma [aldosterone], as well as 4) an increase in urine volume and medullary hypertrophy. The 0K2Na group had the lowest [aldosterone] (172.0 ± 17.4 pg/ml) and lower blood pressure (93.2 ± 4.9 vs. 112.0 ± 3.1 mmHg in 2K2Na). Transporter pool size regulation was determined by quantitative immunoblotting of renal cortex and medulla homogenates. The only differences measured in both 0K1Na and 0K2Na groups were a 20–30% decrease in cortical β-ENaC, 30–40% increases in kidney-specific Ste20/SPS1-related proline/alanine-rich kinase, and a 40% increase in medullary sodium pump abundance. The following proteins were not significantly changed in both the 0 K groups: Na+/H+ exchanger isoform 3; Na+-K+-Cl− cotransporter; Na+-Cl− cotransporter, oxidative stress response kinase-1; renal outer medullary K+ channel; autosomal recessive hypercholesterolemia; c-Src, aquaporin 2 isoform; or renin. Thus, despite profound hypokalemia and renal K+ conservation, we did not confirm many of the changes that were previously reported. We predict that changes in transporter distribution and activity are likely more important for conserving K+ than changes in total abundance.

High-NaCl diets increase natriuretic and diuretic responses in salt-resistant but not salt-sensitive SHR

1991 ◽  
Vol 260 (6) ◽  
pp. F890-F897 ◽  
Author(s):  
M. S. Mozaffari ◽  
S. Jirakulsomchok ◽  
Z. H. Shao ◽  
J. M. Wyss
Keyword(s):  
Arterial Pressure ◽  
Renal Denervation ◽  
Isotonic Saline ◽  
Renal Nerves ◽  
Sprague Dawley ◽  
Volume Loading ◽  
Spontaneously Hypertensive ◽  
Volume Load ◽  
Sprague Dawley Rats ◽  
Wistar Kyoto

This study tested the hypothesis that NaCl-sensitive spontaneously hypertensive rats (SHR-S) display a defect in natriuretic and diuretic responses to acute volume loading that contributes to the rise in arterial pressure observed when the rats are fed a high-NaCl diet. Seven-week-old SHR-S and NaCl-resistant SHR rats (SHR-R) and normotensive (Wistar-Kyoto and Sprague-Dawley rats) were fed high- or basal NaCl diets. After 2.5 wk on the diets, preinstrumented conscious rats received an intravenous infusion (5% body wt; 0.5 ml/min) of isotonic saline, and urine was collected through a bladder catheter for 90 min. Control rats on the high-NaCl diet (compared with basal) excreted a significantly greater percentage of Na+ and volume load. In contrast, SHR-S on high-NaCl diet (compared with basal) had a very small increase in natriuretic response and no increase in diuretic response to volume expansion. The effect of renal denervation on natriuretic and diuretic responses to volume load was tested. In SHR-R on 1 and 8% NaCl diets, renal denervation had little or no effect on these responses, suggesting that renal nerves do not play a prominent role in the dietary NaCl-induced increases in the natriuretic and diuretic responses to volume load. These results demonstrate that NaCl-resistant rats rapidly adapt to diets high in NaCl content with increased natriuretic and diuretic responses to acute volume loading. The failure of SHR-S to adapt to the dietary challenge may result in volume loading and a secondary increase in arterial pressure after feeding.

Mechanism underlying diuretic effect of l-NAME at a subpressor dose

2001 ◽  
Vol 281 (3) ◽  
pp. F414-F419 ◽  
Author(s):  
Mingyu Liang ◽  
Theresa J. Berndt ◽  
Franklyn G. Knox
Keyword(s):  
Proximal Tubule ◽  
Flow Rate ◽  
Nitrate Concentration ◽  
Distal Tubule ◽  
No Synthase ◽  
Urine Flow ◽  
Sprague Dawley ◽  
Sprague Dawley Rats ◽  
Renal Tubular ◽  
Nitrite Nitrate

The diuretic effects of nitric oxide (NO) synthase inhibitors administered at subpressor dose in rats are controversial, and the tubular segments involved are not known. In the present study, we examined the effect of N ω-nitro-l-arginine methyl ester (l-NAME) at a subpressor dose on renal interstitial NO and cGMP activity and on renal tubular segmental reabsorption of fluid in the rat. Intravenous infusion of l-NAME at 1 μg · kg−1 · min−1 in Sprague-Dawley rats ( N = 8), which did not alter mean arterial pressure or glomerular filtration rate, significantly increased urine flow rate (Uv; from 78.2 ± 12.7 to 117.1 ± 14.9 μl/min, P < 0.05). Paradoxically, this effect of l-NAME was concomitant with significant increases in nitrite/nitrate (from 10.79 ± 1.20 to 16.50 ± 2.60 μM, P < 0.05) and cGMP (from 0.65 ± 0.09 to 0.98 ± 0.18 nM, P < 0.05) concentrations in renal cortical microdialysate as well as the nitrite/nitrate concentration in the medullary microdialysate. Micropuncture studies in the superficial nephron revealed that l-NAME significantly increased the flow rate (from 8.3 ± 0.9 to 12.2 ± 1.2 nl/min, P < 0.05) and fractional delivery of fluid to the distal tubule, but not those in the late proximal tubule. In conclusion, l-NAME, at the subpressor dose used in this study, increased renal nitrate/nitrite and cGMP and inhibited fluid reabsorption in tubular segments between the late proximal tubule and the distal tubule of superficial nephrons.

Renal interstitial hydrostatic pressure and pressure natriuresis in pregnant rats

2000 ◽  
Vol 279 (2) ◽  
pp. F353-F357 ◽  
Author(s):  
Ali A. Khraibi
Keyword(s):  
Hydrostatic Pressure ◽  
Perfusion Pressure ◽  
Fractional Excretion ◽  
Normal Pregnancy ◽  
Renal Perfusion ◽  
Sprague Dawley ◽  
Pregnant Rats ◽  
Sprague Dawley Rats ◽  
Fractional Excretion Of Sodium ◽  
Pressure Natriuresis

The objective of this study was to test the hypothesis that a decrease in renal interstitial hydrostatic pressure (RIHP) accounts for the blunted pressure natriuresis during pregnancy. RIHP was measured in nonpregnant (NP; n = 9), midterm pregnant (MP; 12–14 days after conception; n = 10), and late-term pregnant (LP; 18–21 days after conception; n = 12) female Sprague-Dawley rats at two renal perfusion pressure (RPP) levels (99 and 120 mmHg). At the lower RPP level, RIHP was 5.9 ± 0.3 mmHg for NP, 3.4 ± 0.4 mmHg for MP ( P < 0.05 vs. NP), and 2.9 ± 0.1 mmHg for LP ( P < 0.05 vs. NP) rats. The increase in RPP from 99 to 120 mmHg resulted in pressure natriuretic and diuretic responses in all groups; however, the increases in fractional excretion of sodium (ΔFENa), urine flow rate (ΔV), and ΔRIHP were significantly greater ( P < 0.05) in NP compared with both MP and LP rats. ΔFENa, ΔV, and ΔRIHP were 2.06 ± 0.28%, 81.44 ± 14.10 μl/min, and 3.0 ± 0.5 mmHg for NP; 0.67 ± 0.13%, 28.03 ± 5.28 μl/min, and 0.5 ± 0.2 mmHg for MP; and 0.48 ± 0.12%, 18.14 ± 4.70 μl/min, and 0.4 ± 0.1 mmHg for LP rats. In conclusion, RIHP is significantly lower in pregnant compared with nonpregnant rats at similar RPP levels. Also, the ability of pregnant rats to increase RIHP in response to an increase in RPP is blunted. These changes in RIHP may play an important role in the blunted pressure natriuresis and contribute to the conservation of sodium and water that is critical for fetal growth and development during normal pregnancy.

Tubuloglomerular feedback and tubular reabsorption during acute potassium loading in rats

1994 ◽  
Vol 267 (2) ◽  
pp. F223-F230 ◽  
Author(s):  
B. Braam ◽  
P. Boer ◽  
H. A. Koomans
Keyword(s):  
Distal Tubule ◽  
Plasma Potassium ◽  
Tubuloglomerular Feedback ◽  
Control Group ◽  
Sprague Dawley ◽  
Time Control ◽  
Sprague Dawley Rats ◽  
Single Nephron ◽  
Flow Pressure ◽  
Potassium Loading

Acute hyperkalemia has been associated with changes in reabsorption, glomerular filtration rate (GFR), and autoregulation, which might represent altered tubuloglomerular feedback (TGF) responsiveness. Therefore, TGF responsiveness, segmental reabsorption of water, sodium and potassium, and single-nephron GFR were evaluated during acute potassium loading in male Sprague-Dawley rats. Rats receiving 300 mM KNO3, KHCO3, and KCl showed significantly increased plasma potassium levels and attenuation of stop-flow pressure responses 45-90 min after starting the potassium infusion compared with that observed in time controls and rats infused with 300 mM NaCl. Attenuation of TGF responsiveness could not be related to plasma and kidney angiotensin II levels. Segmental water and sodium handling and proximal to distal single-nephron GFR differences assessed in a time control group and a group receiving 300 mM KCl revealed no changes related to KCl infusion. However, late proximal and early distal potassium concentrations increased significantly from 4.7 +/- 0.2 to 6.3 +/- 0.3 mM (P < 0.01) and from 1.5 +/- 0.1 to 2.7 +/- 0.4 mM (P < 0.01), respectively. In summary, although attenuated TGF responsiveness was demonstrated at higher perfusion rates, this study does not support a significant role for either the TGF mechanism or changes in reabsorption upstream of the early distal tubule for the initiation of kaliuresis during acute potassium loading.

Active potassium absorption by the renal distal tubule

1992 ◽  
Vol 262 (3) ◽  
pp. F488-F493 ◽  
Author(s):  
M. D. Okusa ◽  
R. J. Unwin ◽  
H. Velazquez ◽  
G. Giebisch ◽  
F. S. Wright
Keyword(s):  
Distal Tubule ◽  
Sprague Dawley ◽  
Direct Demonstration ◽  
Sprague Dawley Rats ◽  
Potassium Flux ◽  
Low Potassium ◽  
Potassium Absorption ◽  
Transepithelial Voltage ◽  
Distal Tubules

Maintenance of potassium homeostasis during potassium depletion appears to involve an active potassium absorptive mechanism in the distal nephron. Direct demonstration of such a pathway in the distal tubule of the rat has been lacking. The purpose of the current study was to examine the hypothesis that an ATP-dependent active transport mechanism plays a role in potassium absorption by the rat distal tubule. We utilized in vivo microperfusion techniques in Sprague-Dawley rats maintained on a regular diet of low-potassium diet for 3-4 wk. The effect of a selective inhibitor of the gastric H-K-adenosinetriphosphatase (ATPase) (Sch 28080, 0.1 mM) was tested in distal tubules of both groups of rats. Distal tubules of normal rats secreted potassium. Sch 28080 had no effect on this net potassium flux. In contrast, distal tubules of potassium-deficient rats absorbed potassium. Sch 28080 abolished this potassium absorption and produced a small hyperpolarization of the lumen-negative transepithelial voltage (VTE). The change in VTE can be explained by a concomitant increase in potassium concentration in the late distal tubule. These results are consistent with the presence of an H-K-ATPase in the distal tubule of potassium-deficient rats.

Acute Pressure Natriuresis and Na + Transporter Regulation More Robust in Female vs. Male Sprague Dawley Rats

2020 ◽  
Vol 34 (S1) ◽  
pp. 1-1
Author(s):  
Brandon E. McFarlin ◽  
Donna Lee Ralph ◽  
Alicia A. McDonough
Keyword(s):  
Sprague Dawley ◽  
Sprague Dawley Rats ◽  
Pressure Natriuresis

Immunolocalization of ectonucleotidases along the rat nephron

2006 ◽  
Vol 290 (2) ◽  
pp. F550-F560 ◽  
Author(s):  
Renu M. Vekaria ◽  
David G. Shirley ◽  
Jean Sévigny ◽  
Robert J. Unwin
Keyword(s):  
Collecting Duct ◽  
Distal Tubule ◽  
Extracellular Nucleotides ◽  
Thick Ascending Limb ◽  
Sprague Dawley ◽  
Low Level ◽  
Amplification Method ◽  
Sprague Dawley Rats ◽  
Collecting Ducts ◽  
Calbindin D

Evidence is accumulating that extracellular nucleotides act as autocrine/paracrine agents in most tissues, including the kidneys. Several families of surface-located enzymes, collectively known as ectonucleotidases, can degrade nucleotides. Using immunohistochemistry, we have examined the segmental distribution of five ectonucleotidases along the rat nephron. Perfusion-fixed kidneys were obtained from anesthetized male Sprague-Dawley rats. Cryostat sections of cortical and medullary regions were incubated with antibodies specific to the following enzymes: ectonucleoside triphosphate diphosphohydrolase (NTPDase) 1, NTPDase2, NTPDase3, ectonucleotide pyrophosphatase phosphodiesterase 3 (NPP3), and ecto-5′-nucleotidase. Sections were then costained with Phaseolus vulgaris erythroagglutinin (for identification of proximal tubules) and antibodies against Tamm-Horsfall protein (for identification of thick ascending limb), calbindin-D28k (for identification of distal tubule), and aquaporin-2 (for identification of collecting duct). The tyramide signal amplification method was used when the ectonucleotidase and marker antibody were raised in the same species. The glomerulus expressed NTPDase1 and NPP3. The proximal tubule showed prominent expression of NPP3 and ecto-5′-nucleotidase in most, but not all, segments. NTPDase2 and NTPDase3, but not NPP3 or ecto-5′-nucleotidase, were expressed in the thick ascending limb and distal tubule. NTPDase3, with some low-level expression of ecto-5′-nucleotidase, was also found in cortical and outer medullary collecting ducts. Inner medullary collecting ducts displayed low-level staining for NTPDase1, NTPDase2, NTPDase3, and ecto-5′-nucleotidase. We conclude that these ectonucleotidases are differentially expressed along the nephron and may play a key role in activation of purinoceptors by nucleotides and nucleosides.

Blood pressure maintenance in NHE3-deficient mice with transgenic expression of NHE3 in small intestine

2005 ◽  
Vol 288 (3) ◽  
pp. R685-R691 ◽  
Author(s):  
William T. Noonan ◽  
Alison L. Woo ◽  
Michelle L. Nieman ◽  
Vikram Prasad ◽  
Patrick J. Schultheis ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Small Intestine ◽  
Transgenic Expression ◽  
Specific Effects ◽  
Lower Blood ◽  
Blood Pressures ◽  
Pressure Natriuresis ◽  
Deficient Mice ◽  
Robust Response

NHE3 Na+/H+ exchanger knockout ( Nhe3−/−) mice have severe absorptive deficits in the kidney proximal tubule and intestinal tract. The resulting hypovolemia has confounded efforts to carefully evaluate the specific effects of NHE3 deficiency on kidney function. Development of mice with transgenic expression of NHE3 in the small intestine (tg Nhe3−/−) has allowed us to analyze the role of renal NHE3 in overall maintenance of blood pressure, pressure natriuresis, and autoregulation of both glomerular filtration rate (GFR) and renal blood flow (RBF). Ambulatory blood pressure, measured by telemetry, was lower in tg Nhe3−/− mice than in wild-type controls (tg Nhe3+/+) when the mice were maintained on a normal NaCl diet but was normalized when they were provided with a high NaCl intake. Furthermore, administration of the AT1-receptor blocker losartan showed that circulating ANG II plays a major role in maintaining blood pressure in tg Nhe3−/− mice fed normal NaCl but not in those receiving high NaCl. Clearance studies revealed a blunted pressure-natriuresis response in tg Nhe3−/− mice at lower blood pressures but a robust response at higher blood pressures. Autoregulation of GFR and RBF was normal in tg Nhe3−/− mice. These results show that dietary NaCl loading normalizes blood pressure in awake tg Nhe3−/− mice and that alterations in NHE3 activity are not essential for normal autoregulation of GFR and RBF. Furthermore, the data strongly support the hypothesis that NHE3 plays an important role in the diuretic and natriuretic responses to increases in blood pressure but also show that mechanisms not involving NHE3 mediate pressure natriuresis in the higher range of blood pressures studied.

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