scholarly journals Juxtamedullary Nephron

2020 ◽  
Author(s):  
Keyword(s):  
Juxtamedullary Nephron

scholarly journals Potassium channel contributions to afferent arteriolar tone in normal and diabetic rat kidney

2008 ◽  
Vol 295 (1) ◽  
pp. F171-F178 ◽  
Author(s):  
Carmen M. Troncoso Brindeiro ◽  
Rachel W. Fallet ◽  
Pascale H. Lane ◽  
Pamela K. Carmines
Keyword(s):  
Potassium Channel ◽  
Rat Kidney ◽  
The Other ◽  
Diabetic Rat ◽  
Channel Blockers ◽  
Juxtamedullary Nephron ◽  
Afferent Arterioles ◽  
Arteriolar Tone ◽  
Constrictor Response

We previously reported an enhanced tonic dilator impact of ATP-sensitive K+ channels in afferent arterioles of rats with streptozotocin (STZ)-induced diabetes. The present study explored the hypothesis that other types of K+ channel also contribute to afferent arteriolar dilation in STZ rats. The in vitro blood-perfused juxtamedullary nephron technique was utilized to quantify afferent arteriolar lumen diameter responses to K+ channel blockers: 0.1–3.0 mM 4-aminopyridine (4-AP; KV channels), 10–100 μM barium (KIR channels), 1–100 nM tertiapin-Q (TPQ; Kir1.1 and Kir3.x subfamilies of KIR channels), 100 nM apamin (SKCa channels), and 1 mM tetraethylammonium (TEA; BKCa channels). In kidneys from normal rats, 4-AP, TEA, and Ba2+ reduced afferent diameter by 23 ± 3, 8 ± 4, and 18 ± 2%, respectively, at the highest concentrations employed. Neither TPQ nor apamin significantly altered afferent diameter. In arterioles from STZ rats, a constrictor response to TPQ (22 ± 4% decrease in diameter) emerged, and the response to Ba2+ was exaggerated (28 ± 5% decrease in diameter). Responses to the other K+ channel blockers were similar to those observed in normal rats. Moreover, exposure to either TPQ or Ba2+ reversed the afferent arteriolar dilation characteristic of STZ rats. Acute surgical papillectomy did not alter the response to TPQ in arterioles from normal or STZ rats. We conclude that 1) KV, KIR, and BKCa channels tonically influence normal afferent arteriolar tone, 2) KIR channels (including Kir1.1 and/or Kir3.x) contribute to the afferent arteriolar dilation during diabetes, and 3) the dilator impact of Kir1.1/Kir3.x channels during diabetes is independent of solute delivery to the macula densa.

Angiotensin II effects on microvascular diameters of in vitro blood-perfused juxtamedullary nephrons

1986 ◽  
Vol 251 (4) ◽  
pp. F610-F618 ◽  
Author(s):  
P. K. Carmines ◽  
T. K. Morrison ◽  
L. G. Navar
Keyword(s):  
Angiotensin Ii ◽  
Constant Pressure ◽  
Ang Ii ◽  
Experimental Conditions ◽  
Vasoactive Hormones ◽  
Juxtamedullary Nephron ◽  
Single Nephron ◽  
Afferent Arterioles ◽  
Dose Dependent

The purpose of this study was to determine the specific renal microvascular segments that are functionally responsive to angiotensin II (ANG II) and other vasoactive hormones. Experiments were performed on juxtamedullary tissue from captopril-treated rats during perfusion with blood at a constant pressure of 110 mmHg. Epifluorescence videomicroscopy was utilized to measure diameters of arcuate and interlobular arteries (ART), mid- (MA) and late- (LA) afferent arterioles, and efferent arterioles (EA). Norepinephrine (700 nM) significantly decreased, and sodium nitroprusside (380 nM) increased, inside diameters of all segments. Topical application of ANG II (0.01 to 1 nM) induced significant reductions in diameters of all vessel segments: ART, 17.5 +/- 2.0%; MA, 19.6 +/- 2.5%; LA, 13.5 +/- 1.5%; and EA, 16.9 +/- 2.7%. The preglomerular response to ANG II was blocked by saralasin (10 microM) and, in most cases, was dose dependent; however, an initial hypersensitivity to low ANG II doses (30% decrease in diameter) was exhibited by 38% of the preglomerular vessels studied. Under these experimental conditions, single-nephron glomerular filtration rate decreased significantly in response to 0.01 nM ANG II exposure. These observations demonstrate that physiological concentrations of ANG II can elicit receptor-dependent and reversible vasoconstriction of the juxtamedullary nephron microvasculature at both pre- and postglomerular sites.

Direct evaluation of the microvascular actions of ANP in juxtamedullary nephrons

1988 ◽  
Vol 254 (3) ◽  
pp. F440-F444 ◽  
Author(s):  
P. J. Veldkamp ◽  
P. K. Carmines ◽  
E. W. Inscho ◽  
L. G. Navar
Keyword(s):  
Angiotensin Ii ◽  
Topical Administration ◽  
Normal Kidney ◽  
Arterial Diameter ◽  
Direct Evaluation ◽  
Juxtamedullary Nephron ◽  
Afferent Arterioles ◽  
Renal Vascular ◽  
Arteriolar Diameter

The renal vascular actions of atrial natriuretic peptide (ANP) remain incompletely understood. The purpose of this study is to evaluate the effects of ANP on microvascular structures of the normal kidney. The in vitro blood-perfused juxtamedullary nephron technique was utilized to allow visualization of arcuate arteries and afferent and efferent arterioles. Donor rats were pretreated with captopril to eliminate possible interactions between angiotensin II and atriopeptin III (AP III). The effects of topical administration of 3 nM AP III were determined by videometric analysis of vessel inside diameters. Under control conditions, arcuate arterial diameter averaged 83 +/- 14 microns (n = 7), afferent arteriolar diameter was 20 +/- 4 microns (n = 7), and efferent arteriolar diameter was 16 +/- 2 microns (n = 7). During superfusion with AP III, arcuate arteries and afferent arterioles dilated 73 +/- 9 and 23 +/- 5%, respectively. Both returned to their control values when AP III was removed from the superfusate. Further experiments on arcuate arteries (n = 5) revealed that 0.3 nM AP III also vasodilated these vessels (26 +/- 9%); however, no significant effect was elicited by 0.03 nM AP III. In contrast to the vasodilator influence of AP III on preglomerular vessels, efferent arteriolar diameter was not altered by AP III exposure. These observations reveal that AP III can induce selective preglomerular vasodilation involving arcuate arteries as well as afferent arterioles, while efferent arteriolar diameter is not perceptibly influenced.

Effects of ATP on pre- and postglomerular juxtamedullary microvasculature

1992 ◽  
Vol 263 (5) ◽  
pp. F886-F893 ◽  
Author(s):  
E. W. Inscho ◽  
K. Ohishi ◽  
L. G. Navar
Keyword(s):  
Perfusion Pressure ◽  
Renal Perfusion ◽  
Renal Perfusion Pressure ◽  
Organ Systems ◽  
Smooth Muscle Function ◽  
Juxtamedullary Nephron ◽  
Afferent Arterioles ◽  
The Right ◽  
Dose Dependent

Based on evidence that extracellular ATP can influence vascular smooth muscle function in other organ systems, experiments were conducted to characterize the responsiveness of rat juxtamedullary microvascular segments to ATP. Experiments were performed using the in vitro blood-perfused juxtamedullary nephron preparation combined with video microscopy. Pentobarbital-anesthetized rats were pretreated with enalaprilat (2 mg iv) for 30 min before the right kidney was isolated and prepared for study. Renal perfusion pressure was set at 110 mmHg and held constant. Under control conditions, afferent and efferent arteriolar diameters averaged 19.9 +/- 1.4 (n = 19) and 21.6 +/- 1.2 microns (n = 10), respectively. Superfusion with 1, 10, and 100 microM ATP solutions induced sustained dose-dependent afferent vasoconstriction of 8.3 +/- 1.4, 12.8 +/- 1.7, and 12.1 +/- 2.1%, respectively (P < 0.01). Afferent vasoconstrictor responses to ATP were also observed during adenosine receptor blockade. In contrast, efferent arterioles were unresponsive to ATP stimulation even at concentrations as high as 100 microM (P > 0.05). Arcuate and interlobular arterial diameters averaged 82.0 +/- 15.7 (n = 5) and 43.4 +/- 4.5 microns (n = 6), respectively, during control conditions and responded to ATP treatment with a transient vasoconstriction followed by a gradual return to control diameter. Interlobular arteries exhibited a sustained constriction only at the 100 microM concentration (P < 0.05). These data demonstrate that afferent arterioles are more responsive to ATP treatment than other renal microvascular segments and suggest the presence of ATP-sensitive P2x purinoceptors on pre- but not postglomerular juxtamedullary microvascular elements.

Renal cortical necrosis: a model for the study of juxtamedullary nephron physiology.

1974 ◽  
Vol 37 (2) ◽  
pp. 228-234 ◽  
Author(s):  
H A Rashid ◽  
C A Linke ◽  
T Bonfiglio ◽  
M S Wu
Keyword(s):  
Cortical Necrosis ◽  
Renal Cortical Necrosis ◽  
Juxtamedullary Nephron

Direct assessment of renal microvascular responses to P2-purinoceptor agonists

1998 ◽  
Vol 274 (4) ◽  
pp. F718-F727 ◽  
Author(s):  
Edward W. Inscho ◽  
Anthony K. Cook ◽  
Vy Mui ◽  
Jason Miller
Keyword(s):  
Vessel Diameter ◽  
Renal Perfusion ◽  
Receptor Subtypes ◽  
Selective Agonist ◽  
Juxtamedullary Nephron ◽  
Afferent Arterioles ◽  
Arcuate Artery ◽  
Arteriolar Diameter

Studies were performed to determine the responsiveness of rat juxtamedullary afferent arterioles to receptor-selective P2-purinoceptor agonists. Experiments were performed in vitro using the blood perfused juxtamedullary nephron technique, combined with videomicroscopy. Renal perfusion pressure was set at 110 mmHg and held constant. Basal afferent arteriolar diameter averaged 22.0 ± 0.6 μm ( n = 69). Stimulation with 0.1, 1.0, 10, and 100 μM ATP ( n = 10) elicited a concentration-dependent vasoconstriction averaging 8 ± 2, 17 ± 2, 21 ± 4, and 23 ± 5%, respectively. A nearly identical afferent arteriolar vasoconstriction was observed in response to the P2X-selective agonist β,γ-methylene ATP ( n = 10); however, another P2X agonist, α,β-methylene ATP, evoked marked receptor desensitization ( n = 10). Vessel diameter decreased by ∼7 ± 2, 16 ± 2, 23 ± 3, and 22 ± 3%, respectively, over the same concentration range. The P2Y-selective agonist, 2-methylthio-ATP, evoked only a modest vasoconstriction, whereas UTP and adenosine 5′- O-(3-thiotriphosphate) (ATPγS) reduced afferent diameter markedly at concentrations >1.0 μM. Afferent arteriolar diameter decreased by 5 ± 4, 31 ± 8, and 72 ± 8% during UTP administration ( n = 7) at concentrations of 1.0, 10, and 100 μM, respectively. Similarly, ATPγS ( n = 6) decreased afferent diameter by 16 ± 2, 58 ± 8, and 98 ± 3%, respectively, over the same concentration range. Nitric oxide synthesis inhibition with N ω-nitro-l-arginine did not significantly alter the afferent arteriolar response to ATP but did potentiate ATP-mediated arcuate artery vasoconstriction. The following data suggest the presence of multiple P2 receptors on juxtamedullary afferent arterioles and are consistent with classification of those receptors as members of the P2X- and P2Y2 (P2U)-receptor subtypes.

Natriuretic effect of atriopeptin III in rats with papillary necrosis

1989 ◽  
Vol 257 (5) ◽  
pp. F859-F865 ◽  
Author(s):  
J. Garcia-Estan ◽  
K. Takezawa ◽  
R. J. Roman
Keyword(s):  
Blood Flow ◽  
Glomerular Filtration Rate ◽  
Hydrostatic Pressure ◽  
Glomerular Filtration ◽  
Sodium Excretion ◽  
Filtration Rate ◽  
Renal Papilla ◽  
Papillary Necrosis ◽  
Juxtamedullary Nephron ◽  
Natriuretic Effect

This study compared the effects of atriopeptin III (AP III) on sodium excretion and renal interstitial hydrostatic pressure (RIHP) in control rats and in rats pretreated with 2-bromoethylamine (BEA) to produce papillary necrosis. In control rats, infusion of AP III (100 ng.kg-1.min-1) increased sodium excretion from 2.2 +/- 0.7 to 6.4 +/- 0.9 microeq.min-1.g kidney wt-1 and RIHP from 6.8 +/- 0.7 to 8.7 +/- 0.9 mmHg, whereas glomerular filtration rate and renal blood flow were unaltered. Similar results were obtained in rats pretreated with BEA 48 h before the experiment. In rats studied 6 wk after BEA treatment, the papilla was absent and there was atrophy of juxtamedullary nephrons. AP III did not alter sodium excretion or RIHP in this group of rats. These results indicate that 1) an intact renal papilla and/or juxtamedullary nephron population may be required for the natriuretic effect of AP III; 2) the papillary injury 48 h after BEA is not sufficient to abolish the natriuretic response to AP III; and 3) elevations in RIHP may play a role in the natriuretic response to AP III.

scholarly journals Heme oxygenase induction attenuates afferent arteriolar autoregulatory responses

2008 ◽  
Vol 295 (4) ◽  
pp. F904-F911 ◽  
Author(s):  
Fady T. Botros ◽  
Minolfa C. Prieto-Carrasquero ◽  
Victoria L. Martin ◽  
L. Gabriel Navar
Keyword(s):  
Epithelial Cells ◽  
Perfusion Pressure ◽  
Soluble Guanylate Cyclase ◽  
Renal Perfusion ◽  
Tubular Epithelial Cells ◽  
Renal Autoregulation ◽  
Heme Oxygenases ◽  
Renal Perfusion Pressure ◽  
Weak Staining ◽  
Juxtamedullary Nephron

Heme oxygenases (HO-1, HO-2) catalyze conversion of heme to iron, carbon monoxide (CO), and biliverdin/bilirubin. We studied the effects of renal HO-1 induction on afferent arteriole (Aff-Art) autoregulatory responses to increases in renal perfusion pressure (RPP). Rats were treated with hemin and SnCl2 to induce HO-1, and Aff-Art autoregulatory responses were evaluated using the rat blood-perfused juxtamedullary nephron preparation. Renal HO-1 expression was significantly increased in hemin- and SnCl2-treated rats, while HO-2 was not altered. Aff-Art autoregulatory constrictor responses to increases in RPP from 100 to 150 mmHg were attenuated in hemin- and SnCl2-treated rats compared with control rats (+1.1 ± 3.3, n = 9 and +4.4 ± 5.3, n = 9 vs. −14.2 ± 1.5%, n = 10, respectively) ( P < 0.05). Acute HO inhibition with chromium mesoporphyrin (CrMP; 15 μmol/l) restored Aff-Art autoregulatory responses in hemin- and SnCl2-treated rats. Superfusing Aff-Arts from control rats with 100 μmol/l biliverdin did not alter autoregulatory responses; however, superfusion with 1 mmol/l CO significantly attenuated autoregulatory responses to increases in RPP from 100 to 150 mmHg (+3.3 ± 5.4 vs. −16.6 ± 3.8%, n = 6) ( P < 0.05). Acute soluble guanylate cyclase inhibition with 10 μmol/l ODQ restored Aff-Art autoregulatory responses in hemin-treated rats. Immunohistochemistry shows HO-2 to be expressed mainly in epithelial cells with weak staining in proximal tubules, interlobular arteries, and Aff-Arts. In hemin- and SnCl2-treated rats, HO-1 was induced in tubular epithelial cells but not interlobular arteries and Aff-Arts. We conclude that induction of renal HO-1 attenuates Aff-Art constrictor responses to increases in RPP via increasing CO production from tubular epithelial cells, suggesting that an augmented HO system in pathophysiological conditions modulates renal autoregulation.

scholarly journals Superficial and Juxtamedullary Nephron Function during Saline Loading in the Dog

1974 ◽  
Vol 53 (4) ◽  
pp. 971-979 ◽  
Author(s):  
Frank J. Bruns ◽  
Edward A. Alexander ◽  
Arthur L. Riley ◽  
Norman G. Levinsky
Keyword(s):  
Saline Loading ◽  
Juxtamedullary Nephron

Model of ammonium and bicarbonate transport along LDL: implications for alkalinization of luminal fluid

1993 ◽  
Vol 264 (3) ◽  
pp. F397-F403 ◽  
Author(s):  
R. Mejia ◽  
M. F. Flessner ◽  
M. A. Knepper
Keyword(s):  
Mathematical Model ◽  
Water Permeability ◽  
Dominant Role ◽  
Proximal Convoluted Tubule ◽  
Bicarbonate Transport ◽  
Osmotic Water Permeability ◽  
Water Abstraction ◽  
Osmotic Water ◽  
Juxtamedullary Nephron

Luminal fluid exiting the proximal convoluted tubule of a juxtamedullary nephron is alkalinized as it passes through the long-loop thin descending limb of Henle (LDL). Three potential mechanisms of alkalinization are: 1) concentration of bicarbonate by water abstraction, 2) direct bicarbonate entry, and 3) NH3 entry. We have used a mathematical model of the LDL to investigate these mechanisms. With permeabilities of HCO3-, NH3, and NH4+ measured for subsegments of the chinchilla LDL [M. F. Flessner, R. Mejia, and M. A. Knepper. Am. J. Physiol. 264 (Renal Fluid Electrolyte Physiol. 33):F388-F396, 1993], the osmotic water permeability of each segment [C.-L. Chou and M. A. Knepper. Am. J. Physiol. 263 (Renal Fluid Electrolyte Physiol. 32):F417-F426, 1992], and appropriate parameters from the literature, we have used the model to calculate hypothetical pH, HCO3- concentration, and NH3 concentration of the luminal fluid as it descends the LDL within an assumed interstitium. After eliminating each mechanism in turn by setting the appropriate permeability to zero, we recalculated the axial profiles. Our results suggest that, although all three mechanisms individually contribute to LDL alkalinization, NH3 entry likely plays the dominant role.

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