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

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

Circulation ◽

10.1161/circ.132.suppl_3.16993 ◽

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.

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Renal interstitial hydrostatic pressure and pressure natriuresis in pregnant rats

AJP Renal Physiology ◽

10.1152/ajprenal.2000.279.2.f353 ◽

2000 ◽

Vol 279 (2) ◽

pp. F353-F357 ◽

Cited By ~ 13

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.

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Pressure natriuresis following acute and chronic inhibition of nitric oxide synthase in rats

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1996.270.2.r469 ◽

1996 ◽

Vol 270 (2) ◽

pp. R469-R478 ◽

Cited By ~ 9

Author(s):

G. R. Guarasci ◽

R. L. Kline

Keyword(s):

Nitric Oxide ◽

Hydrostatic Pressure ◽

Nitric Oxide Synthase ◽

Chronic Administration ◽

Acute Administration ◽

Sprague Dawley ◽

Sprague Dawley Rats ◽

Pressure Natriuresis ◽

Oxide Synthase ◽

The Relationship

Nitric oxide has been suggested to be an essential mediator of pressure natriuresis. To investigate this hypothesis, the effect of acute or chronic inhibition of nitric oxide synthase on pressure natriuresis and renal interstitial hydrostatic pressure was studied in anesthetized Sprague-Dawley rats with fixed neural and hormonal influences on the kidney. Both acute infusion (10 micrograms.kg-1.min-1 iv) and chronic administration (50 mg.kg-1.day-1 for 7 days in drinking water) of NG-nitro-L-arginine methyl ester (L-NAME) resulted in significantly increased mean arterial pressure, a 30% decrease in renal blood flow, and no change in glomerular filtration rate when compared with values in control rats. Pressure-diuresis, pressure-natriuresis, and pressure-fractional sodium excretion curves in L-NAME-treated rats were shifted to a higher pressure (by approximately 25 mmHg) when compared with those in control rats. The relationship between renal artery pressure and renal interstitial hydrostatic pressure was shifted similarly in L-NAME-treated rats. Acute administration of L-arginine completely reversed the renal effects of chronic L-NAME. These data indicate that, at the doses used in this study, both acute and chronic inhibition of nitric oxide synthase decreased the ability of the kidney to excrete sodium at least in part by a hemodynamic mechanism leading to an increased filtration fraction and a decreased renal interstitial pressure. The parallel shift of the pressure-natriuresis curve to a higher pressure suggests that nitric oxide is an important modulator but not an essential mediator of the pressure natriuresis.

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Detection of apical Na+/H+exchanger activity inhibition in proximal tubules induced by acute hypertension

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.2000.279.4.r1412 ◽

2000 ◽

Vol 279 (4) ◽

pp. R1412-R1418 ◽

Cited By ~ 22

Author(s):

Kay-Pong Yip ◽

Anthony J. Wagner ◽

Donald J. Marsh

Keyword(s):

Rate Of Change ◽

Proximal Tubules ◽

High Temporal Resolution ◽

Sprague Dawley ◽

Acute Hypertension ◽

Sprague Dawley Rats ◽

Fluorescence Dye ◽

Pressure Natriuresis ◽

Acute Changes

We previously showed that acute arterial hypertension induces an inhibition of fluid and NaCl reabsorption in proximal tubules of Sprague-Dawley rats, which is associated with a rapid reversible internalization of apical Na+/H+ exchanger in brush border. To determine whether there is a corresponding inhibition of apical Na+/H+ exchanger activity in proximal tubules to account for the reduced tubular reabsorption, an instrument capable of measuring intracellular pH (pHi) ratiometrically and repeatedly on the surface of kidney with high temporal resolution is required. We report the design and validation of such a fluorimetric system based on two ultraviolet nitrogen-pulsed lasers and a photomultiplier. pHi of proximal tubules in situ was measured with pH-sensitive fluorescence dye 2′,7′-bis(2-carboxyethyl)-5(6)-carboxyfluorescein at 5 Hz. Using the initial rate of change of pHi(dpHi/d t) during luminal Na+ removal as an index of apical Na+/H+ exchanger activity, the exchanger activity was found to be reduced by 52 ± 11% (n = 14, P < 0.05) compared with the baseline after 20 min of induced acute hypertension. The inhibition of Na+/H+ exchange activity was alleviated when the blood pressure was returned to prehypertensive level. These observations indicate that acute changes in arterial pressure can reversibly inhibit apical Na+/H+ exchanger activity, which might contribute to pressure natriuresis in proximal tubule.

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Expression and actions of HIF prolyl-4-hydroxylase in the rat kidneys

AJP Renal Physiology ◽

10.1152/ajprenal.00457.2005 ◽

2007 ◽

Vol 292 (1) ◽

pp. F207-F216 ◽

Cited By ~ 46

Author(s):

Ningjun Li ◽

Fan Yi ◽

Christina M. Sundy ◽

Li Chen ◽

Molly L. Hilliker ◽

...

Keyword(s):

Hypoxia Inducible Factor ◽

Renal Medulla ◽

Renal Perfusion ◽

Mrna Levels ◽

Sprague Dawley ◽

Sprague Dawley Rats ◽

Pressure Natriuresis ◽

Oxide Synthase ◽

Immunohistochemical Analyses ◽

Renal Medullary Function

Hypoxia inducible factor (HIF) prolyl-4-hydroxylase domain-containing proteins (PHDs) promote the degradation of HIF-1α. Because HIF-1α is highly expressed in the renal medulla and HIF-1α-targeted genes such as nitric oxide synthase, cyclooxygenase, and heme oxygenase are important in the regulation of renal medullary function, we hypothesized that PHD regulates HIF-1α levels in the renal medulla and, thereby, participates in the control of renal Na+ excretion. Using real-time RT-PCR, Western blot, and immunohistochemical analyses, we have demonstrated that all three isoforms of PHD, PHD1, PHD2, and PHD3, are expressed in the kidneys and that PHD2 is the most abundant isoform. Regionally, all PHDs exhibited much higher levels in renal medulla than cortex. A furosemide-induced increase in renal medullary tissue Po2 significantly decreased PHD levels in renal medulla, whereas hypoxia significantly increased mRNA levels of PHDs in cultured renal medullary interstitial cells, indicating that O2 regulates PHDs. Functionally, the PHD inhibitor l-mimosine (l-Mim, 50 mg·kg−1·day−1 ip for 2 wk) substantially upregulated HIF-1α expression in the kidneys, especially in the renal medulla, and remarkably enhanced (by >80%) the natriuretic response to renal perfusion pressure in Sprague-Dawley rats. Inhibition of HIF transcriptional activity by renal medullary transfection of HIF-1α decoy oligodeoxynucleotides attenuated l-Mim-induced enhancement of pressure natriuresis, which confirmed that HIF-1α mediated the effect of l-Mim. These results indicate that highly expressed PHDs in the renal medulla make an important contribution to the control of renal Na+ excretion through regulation of HIF-1α and its targeted genes.

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

AJP Renal Physiology ◽

10.1152/ajprenal.00183.2013 ◽

2013 ◽

Vol 305 (4) ◽

pp. F510-F519 ◽

Cited By ~ 54

Author(s):

Mien T. X. Nguyen ◽

Donna H. Lee ◽

Eric Delpire ◽

Alicia A. McDonough

Keyword(s):

Proximal Tubule ◽

Collecting Duct ◽

Urine Volume ◽

Differential Regulation ◽

Ang Ii ◽

Distal Nephron ◽

Sprague Dawley ◽

Sprague Dawley Rats ◽

Medullary Collecting Duct ◽

Pressure Natriuresis

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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Ultrastructural Investigation of Spontaneous Pituitary Adenomas in Aging Sprague-Dawley Rats

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100053747 ◽

1982 ◽

Vol 40 ◽

pp. 216-217

Author(s):

D. J. McComb ◽

J. Beri ◽

F. Zak ◽

K. Kovacs

Keyword(s):

Microscopic Study ◽

Pituitary Adenomas ◽

Wistar Rats ◽

Microscopic Level ◽

Sprague Dawley ◽

Prolactin Cells ◽

Light Microscopic Level ◽

Ultrastructural Investigation ◽

Sprague Dawley Rats ◽

Long Evans

Investigation of the spontaneous pituitary adenomas in rat have been limited mainly to light microscopic study. Furth et al. (1973) described them as chromophobic, secreting prolactin. Kovacs et al. (1977) in an ul trastructural investigation of adenomas of old female Long-Evans rats, found that they were composed of prolactin cells. Berkvens et al. (1980) using immunocytochemistry at the light microscopic level, demonstrated that some spontaneous tumors of old Wistar rats could contain GH, TSH or ACTH as well as PRL.

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Early Development of Drug-Induced Hepatic Necrosis

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100066942 ◽

1971 ◽

Vol 29 ◽

pp. 576-577

Author(s):

F. G. Zaki ◽

E. Detzi ◽

C. H. Keysser

Keyword(s):

Early Development ◽

Hepatic Necrosis ◽

Screening Tests ◽

Dense Matrix ◽

Sprague Dawley ◽

Electron Microscopic ◽

Drug Induced ◽

Hepatocellular Damage ◽

Sprague Dawley Rats ◽

Microscopic Studies

This study represents the first in a series of investigations carried out to elucidate the mechanism(s) of early hepatocellular damage induced by drugs and other related compounds. During screening tests of CNS-active compounds in rats, it has been found that daily oral administration of one of these compounds at a dose level of 40 mg. per kg. of body weight induced diffuse massive hepatic necrosis within 7 weeks in Charles River Sprague Dawley rats of both sexes. Partial hepatectomy enhanced the development of this peculiar type of necrosis (3 weeks instead of 7) while treatment with phenobarbital prior to the administration of the drug delayed the appearance of necrosis but did not reduce its severity.Electron microscopic studies revealed that early development of this liver injury (2 days after the administration of the drug) appeared in the form of small dark osmiophilic vesicles located around the bile canaliculi of all hepatocytes (Fig. 1). These structures differed from the regular microbodies or the pericanalicular multivesicular bodies. They first appeared regularly rounded with electron dense matrix bound with a single membrane. After one week on the drug, these vesicles appeared vacuolated and resembled autophagosomes which soon developed whorls of concentric lamellae or cisterns characteristic of lysosomes (Fig. 2). These lysosomes were found, later on, scattered all over the hepatocytes.

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