Effect of acetylcholine and secretin on medullary collecting duct function in the rat

1986 ◽  
Vol 64 (1) ◽  
pp. 62-65 ◽  
Author(s):  
D. R. Wilson ◽  
U. Honrath ◽  
H. Sonnenberg
Keyword(s):  
Control Function ◽  
Collecting Duct ◽  
Tubular Reabsorption ◽  
Arterial Infusion ◽  
Nephron Segments ◽  
Transport Effect ◽  
Nephron Segment ◽  
Anaesthetized Rats ◽  
Medullary Collecting Duct ◽  
Terminal Nephron

Microcatheterization was used to study the effect of renal arterial infusion of acetylcholine or secretin on medullary collecting duct function in anaesthetized rats. Acetylcholine infusion was associated with natriuresis and increased sodium delivery to, and decreased reabsorption in, the collecting duct. No changes from control function were found with secretin. Renal blood flow was increased with acetylcholine (+82%, p < 0.001), but unchanged with secretin (+15%, nonsignificant). We conclude that acetylcholine natriuresis is due to inhibition of tubular reabsorption of sodium in the medullary collecting duct, as well as in upstream nephron segments. While the latter may be hemodynamically mediated, the former indicates a direct transport effect of the hormone in the terminal nephron segment.

scholarly journals Presence and regulation of Raf-1-K (Kinase), MAPK-K, MAP-K, and S6-K in rat nephron segments.

1995 ◽  
Vol 6 (6) ◽  
pp. 1565-1577
Author(s):  
Y Terada ◽  
T Yamada ◽  
M Takayama ◽  
H Nonoguchi ◽  
S Sasaki ◽  
...  
Keyword(s):  
Growth Factor ◽  
Kinase Inhibitor ◽  
Collecting Duct ◽  
Mitogen Activated Protein Kinase ◽  
Thick Ascending Limb ◽  
Nephron Segments ◽  
Igf I ◽  
Nephron Segment ◽  
Medullary Collecting Duct ◽  
K Activity

Renal nephron segments are heterogeneous, and receptors for endothelin (ET)-1, ET-3, Angiotensin II (AII), epidermal growth factor (EGF), and insulin-like growth factor I distribute differently along the nephron segments. Recently, growth factors and vasoactive substances are reported to stimulate mitogen-activated protein kinase (MAP-K). In this study, we showed that mRNA and proteins of MEK-K, Raf-1-K, MAPK-K, MAP-K (p42 and p44), and S6-K are expressed ubiquitously in intact nephron segment. We demonstrated that four tiers of a cascade composed of the Raf-1-K, MAP-K, MAP-K, and S6-K are stimulated by ET-1 and ET-3 in rat intact glomeruli (Glm) via primarily B-type ET receptors and PKC. The stimulatory effect of EGF and IGF-I to MAP-K activity is inhibited by a tyrosine kinase inhibitor in Glm. IGF-I significantly stimulates MAP-K activity and EGF and All moderately stimulate MAP-K activity in the proximal convoluted tubule (PCT). EGF significantly increased MAP-K cascades and ET-1 and ET-3 slightly increased MAP-K cascades in the medullary thick ascending limb (MTAL). EGF significantly stimulated MAP-K cascades, and ET-1 and ET-3 moderately stimulate MAP-K cascades in the outer medullary collecting duct (OMCD) and the inner medullary collecting duct (IMCD). MAPK-K and S6-K are similarly stimulated by these agonists in each segment. This study shows that MAP-K cascades are expressed in every nephron segment. ET-1, ET-3, All, EGF, and IGF-I stimulate MAP-K cascades heterogeneously along the nephron segment. It was concluded that MAP-K cascades play an important role in the regulation of renal function.

Regional and segmental localization of AE2 anion exchanger mRNA and protein in rat kidney

1995 ◽  
Vol 269 (4) ◽  
pp. F461-F468 ◽  
Author(s):  
F. C. Brosius ◽  
K. Nguyen ◽  
A. K. Stuart-Tilley ◽  
C. Haller ◽  
J. P. Briggs ◽  
...  
Keyword(s):  
Collecting Duct ◽  
Rat Kidney ◽  
Chloride Concentration ◽  
Transepithelial Transport ◽  
Thick Ascending Limb ◽  
Cortical Collecting Duct ◽  
Base Exchange ◽  
Medullary Thick Ascending Limb ◽  
Nephron Segment ◽  
Medullary Collecting Duct

Chloride/base exchange activity has been detected in every mammalian nephron segment in which it has been sought. However, in contrast to the Cl-/HCO3- exchanger AE1 in type A intercalated cells, localization of AE2 within the kidney has not been reported. We therefore studied AE2 expression in rat kidney. AE2 mRNA was present in cortex, outer medulla, and inner medulla. Semiquantitative polymerase chain reaction of cDNA from microdissected tubules revealed AE2 cDNA levels as follows [copies of cDNA derived per mm tubule (+/- SE)]: proximal convoluted tubule, 688 +/- 161; proximal straight tubule, 652 +/- 189; medullary thick ascending limb, 1,378 +/- 226; cortical thick ascending limb, 741 +/- 24; cortical collecting duct, 909 +/- 71; and outer medullary collecting duct, 579 +/- 132. AE2 cDNA was also amplified in thin limbs and in inner medullary collecting duct. AE2 polypeptide was detected in all kidney regions. AE2 mRNA and protein were also detected in several renal cell lines. The data are compatible with the postulated roles of AE2 in maintenance of intracellular pH and chloride concentration and with its possible participation in transepithelial transport.

Cell-specific expression of amiloride-sensitive, Na(+)-conducting ion channels in the kidney

1996 ◽  
Vol 271 (4) ◽  
pp. C1303-C1315 ◽  
Author(s):  
F. Ciampolillo ◽  
D. E. McCoy ◽  
R. B. Green ◽  
K. H. Karlson ◽  
A. Dagenais ◽  
...  
Keyword(s):  
Cell Lines ◽  
Collecting Duct ◽  
Extracellular Fluid ◽  
Cation Channel ◽  
Thick Ascending Limb ◽  
Distal Nephron ◽  
Rt Pcr ◽  
Specific Expression ◽  
Nephron Segments ◽  
Medullary Collecting Duct

Amiloride-sensitive, electrogenic Na+ absorption across the distal nephron plays a vital role in regulating extracellular fluid volume and blood pressure. Recently, two amiloride-sensitive, Na(+)-conducting ion channel cDNAs were cloned. One, an epithelial Na(+)-selective channel (ENaC), is responsible for Na+ absorption throughout the distal nephron. The second, a guanosine 3',5'-cyclic monophosphate (cGMP)-inhibitable cation channel, is conductive to Na+ and Ca2+ and contributes to Na+ absorption across the inner medullary collecting duct (IMCD). As a first step toward understanding the segment-specific contributions(s) of cGMP-gated cation channels and ENaC to Na+ and Ca2+ uptake along the nephron, we used in situ reverse transcription-polymerase chain reaction (RT-PCR) hybridization, solution-phase RT-PCR, and Western blot analysis to examine the nephron and cell-specific expression of these channels in mouse kidney cell lines and/or dissected nephron segments. cGMP-gated cation channel mRNA was detected in proximal tubule, medullary thick ascending limb (mTAL), distal convoluted tubule (DCT), cortical collecting duct (CCD), outer medullary collecting duct (OMCD), and IMCD. cGMP-gated cation channel protein was detected in DCT, CCD, and IMCD cell lines. These observations suggest that hormones that modulate intracellular cGMP levels may regulate Na+, and perhaps Ca2+, uptake throughout the nephron. mRNA for alpha-mENaC, a subunit of the mouse ENaC, was detected in mTAL, DCT, CCD, OMCD, and IMCD. Coexpression of alpha-mENaC and cGMP-gated cation channel mRNAs in mTAL, DCT, CCD, OMCD, and IMCD suggests that both channels may contribute to Na+ absorption in these nephron segments.

Autocrine role of endothelin in rat IMCD: inhibition of AVP-induced cAMP accumulation

1993 ◽  
Vol 265 (1) ◽  
pp. F126-F129 ◽  
Author(s):  
D. E. Kohan ◽  
A. K. Hughes
Keyword(s):  
Arginine Vasopressin ◽  
Collecting Duct ◽  
Camp Accumulation ◽  
Semipermeable Membranes ◽  
Endothelin 1 ◽  
Cyclic Monophosphate ◽  
Nephron Segment ◽  
Specific Receptors ◽  
Medullary Collecting Duct

Exogenous endothelin-1 (ET-1) inhibits arginine vasopressin (AVP)-induced adenosine 3',5'-cyclic monophosphate (cAMP) accumulation in the inner medullary collecting duct (IMCD). Since ET-1 is produced by, and binds to specific receptors on, the IMCD, the possibility exists that ET-1 is an autocrine regulator of AVP action in this nephron segment. To test this hypothesis, rat IMCD cells grown on semipermeable membranes were exposed to rabbit anti-ET antisera or nonimmune rabbit sera (NRS). AVP (10(-9)M) caused a significantly greater accumulation of cAMP in confluent IMCD monolayers preincubated in ET-1 antisera compared with NRS. ET-1 (10(-8) M) inhibited the AVP-induced rise in cAMP by 65% in cells preincubated in ET-1 antisera, but had no effect in NRS-treated cells. Finally, 125I-ET-1 (30 pM) binding was increased sixfold in IMCD preincubated in anti-ET-1 antisera. These data indicate that ET causes tonic autocrine inhibition of AVP responsiveness in the IMCD.

scholarly journals Carbonic anhydrase II and IV mRNA in rabbit nephron segments: stimulation during metabolic acidosis

1998 ◽  
Vol 274 (2) ◽  
pp. F259-F267 ◽  
Author(s):  
Shuichi Tsuruoka ◽  
Ann M. Kittelberger ◽  
George J. Schwartz
Keyword(s):  
Metabolic Acidosis ◽  
Carbonic Anhydrase ◽  
Mrna Expression ◽  
Collecting Duct ◽  
Proximal Tubules ◽  
Rabbit Kidney ◽  
Rt Pcr ◽  
Chronic Metabolic Acidosis ◽  
Nephron Segments ◽  
Medullary Collecting Duct

Carbonic anhydrase (CA) facilitates renal bicarbonate reabsorption and acid excretion. Cytosolic CA II catalyzes the buffering of intracellular hydroxyl ions by CO2, whereas membrane-bound CA IV catalyzes the dehydration of carbonic acid generated from the secretion of protons. Although CA II and IV are expressed in rabbit kidney, it is not entirely clear which segments express which isoforms. It was the purpose of this study to characterize the expression of CA II and CA IV mRNAs by specific segments of the nephron using semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) and to determine the effect of chronic metabolic acidosis on CA expression by those segments. Individual nephron segments (usually 1–2 mm) were isolated by microdissection and subjected to RT-PCR. Amplification was performed simultaneously for CA IV, CA II, and malate dehydrogenase (MDH), a housekeeping gene. The intensities of the PCR products were quantitated by densitometry. CA IV mRNA was expressed by S1 and S2 proximal tubules and by outer medullary collecting duct from inner stripe (OMCDi) and outer stripe and initial inner medullary collecting duct (IMCDi). CA II mRNA was expressed by S1, S2, and S3 proximal tubules, thin descending limb, connecting segment (CNT), and all collecting duct segments. Acid loading induced CA IV mRNA expression in S1 and S2 proximal tubules and in OMCDi and IMCDi. CA II mRNA was induced by acidosis in all three proximal segments and nearly all distal segments beginning with CNT. No upregulation of MDH mRNA expression occurred. These adaptive increases in CA II and IV mRNAs are potentially important in the kidney’s adaptation to chronic metabolic acidosis.

Effects of increased perfusion pressure on medullary collecting duct function

1990 ◽  
Vol 68 (3) ◽  
pp. 402-407 ◽  
Author(s):  
H. Sonnenberg ◽  
U. Honrath ◽  
D. R. Wilson
Keyword(s):  
Sodium Chloride ◽  
Perfusion Pressure ◽  
Collecting Duct ◽  
Time Control ◽  
Bilateral Carotid ◽  
Anaesthetized Rats ◽  
Acute Increase ◽  
Medullary Collecting Duct ◽  
Pressure Natriuresis

The role of the medullary collecting duct in pressure natriuresis has not been established. In vivo microcatheterization was used to study the effect of an acute increase in blood pressure induced by bilateral carotid artery and vagal nerve ligation on medullary collecting duct function in anaesthetized rats. Increased fluid and electrolyte excretion during pressure natriuresis were accompanied by increased delivery of water, sodium, chloride, and potassium to the beginning of the medullary collecting duct, a change that was significantly greater than in a second series of time-control animals. These increases in delivery were within the range for which constant fractional NaCl reabsorption had been found previously. However, during increased perfusion pressure, reabsorption of both sodium and chloride in the medullary collecting duct as a fraction of delivered load were reduced from 81 ± 4.1 to 51 ± 9.3% (p < 0.01) and from 65.7 ± 6.0 to 42.7 ± 9.1% (p < 0.01), respectively. No significant changes in medullary collecting reabsorption were seen in the time controls. We conclude that increased perfusion pressure, in addition to increasing delivery to the medullary collecting duct, also inhibits sodium chloride reabsorption in this nephron segment.Key words: hypertension, vagotomy, collecting duct, sodium excretion, atrial natriuretic factor.

Collecting duct function in cis-platinum nephrotoxicity

1987 ◽  
Vol 65 (6) ◽  
pp. 1200-1204 ◽  
Author(s):  
Douglas R. Wilson ◽  
Ursula Honrath
Keyword(s):  
Sodium Chloride ◽  
Collecting Duct ◽  
Chloride Concentration ◽  
Water Reabsorption ◽  
Pars Recta ◽  
Anaesthetized Rats ◽  
Medullary Collecting Duct ◽  
In Cis ◽  
Tissue Sodium ◽  
Urine Concentrating Ability

Microcatheterization was used to study the effect of cis-platinum nephrotoxicity on inner medullary collecting duct function in anaesthetized rats. Osmolality of collecting duct fluid increased from the beginning to the end (papillary tip) of the collecting duct by only 69 ± 11 mosmol/kg in cis-platinum treated rats (at 5–6 days) compared with 306 ± 75 mosmol/kg in sham controls (p < 0.01). Tubular fluid to plasma inulin concentration ratio was reduced at the beginning and end of the collecting duct. Tubular fluid sodium, chloride, and potassium concentrations were lower at the papillary tip in cis-platinum treated rats (p < 0.01). The results indicate that collecting duct water reabsorption is reduced, but electrolyte reabsorption is normal (or even increased) in cis-platinum nephrotoxicity. Papillary tissue sodium chloride concentration was reduced in cis-platinum treated rats. We conclude that the characteristic decrease in urine concentrating ability in cis-platinum nephrotoxicity is not primarily the result of an intrinsic abnormality in collecting duct function but is secondary to decreased papillary hypertonicity resulting from impaired function in more proximal nephron segments, presumably the pars recta of the proximal tubule and the loop of Henle where previous studies have demonstrated abnormal function.

scholarly journals A mathematical model of the inner medullary collecting duct of the rat: acid/base transport

1998 ◽  
Vol 274 (5) ◽  
pp. F856-F867 ◽  
Author(s):  
Alan M. Weinstein
Keyword(s):  
Mathematical Model ◽  
Acid Secretion ◽  
Collecting Duct ◽  
Model Calculations ◽  
Principal Mode ◽  
Inner Medullary Collecting Duct ◽  
Tubule Lumen ◽  
Nephron Segment ◽  
The Face ◽  
Medullary Collecting Duct

A mathematical model of the inner medullary collecting duct (IMCD) of the rat has been developed that is suitable for simulating luminal buffer titration and ammonia secretion by this nephron segment. Luminal proton secretion has been assigned to an H-K-ATPase, which has been represented by adapting the kinetic model of the gastric enzyme by Brzezinski et al. (P. Brzezinski, B. G. Malmstrom, P. Lorentzon, and B. Wallmark. Biochim. Biophys. Acta 942: 215–219, 1988). In shifting to a 2 H+:1 ATP stoichiometry, the model enzyme can acidify the tubule lumen ∼3 pH units below that of the cytosol, when luminal K+ is in abundance. Peritubular base exit is a combination of ammonia recycling and[Formula: see text] flux (either via[Formula: see text] exchange or via a Cl− channel). Ammonia recycling involves[Formula: see text] uptake on the Na-K-ATPase followed by diffusive NH3 exit [S. M. Wall. Am. J. Physiol. 270 ( Renal Physiol. 39): F432–F439, 1996]; model calculations suggest that this is the principal mode of base exit. By virtue of this mechanism, the model also suggests that realistic elevations in peritubular K+ concentration will compromise IMCD acid secretion. Although ammonia recycling is insensitive to carbonic anhydrase (CA) inhibition, the base exit linked to [Formula: see text] flux provides a CA-sensitive component to acid secretion. In model simulations, it is observed that increased luminal NaCl entry increases ammonia cycling but decreases peritubular [Formula: see text]exchange (due to increased cell Cl−). This parallel system of peritubular base exit stabilizes acid secretion in the face of variable Na+ reabsorption.

Furosemide action on collecting ducts: effect of prostaglandin synthesis inhibition

1983 ◽  
Vol 244 (6) ◽  
pp. F666-F673 ◽  
Author(s):  
D. R. Wilson ◽  
U. Honrath ◽  
H. Sonnenberg
Keyword(s):  
Collecting Duct ◽  
Prostaglandin Synthesis ◽  
Water Reabsorption ◽  
Inner Medullary Collecting Duct ◽  
Nephron Segments ◽  
Inhibit Prostaglandin Synthesis ◽  
Collecting Ducts ◽  
Inhibition Of Prostaglandin Synthesis ◽  
Medullary Collecting Duct ◽  
Furosemide Administration

The effect of furosemide on inner medullary collecting duct chloride reabsorption has not been determined, and the blunting of furosemide action by drugs that inhibit prostaglandin synthesis, while known to occur, has not been examined in detail. The effect of indomethacin and meclofenamate on furosemide diuresis was studied in the rat using clearance and collecting duct microcatheterization methods. Furosemide-treated control animals showed complete inhibition of chloride, sodium, and water reabsorption in the inner medullary collecting duct. Rats given indomethacin or meclofenamate before and during furosemide administration showed marked reduction of the chloriuresis, natriuresis, and diuresis. Reduced delivery of sodium and chloride to the beginning of the inner medullary collecting duct, associated with a decrease in glomerular filtration rate and increased reabsorption in more proximal nephron segments, was largely responsible for the reduced natriuresis and chloriuresis during inhibition of prostaglandin synthesis. In addition, indomethacin increased collecting duct NaCl reabsorption toward normal, but meclofenamate showed no such effect. The results indicate that furosemide inhibits medullary collecting duct reabsorption of chloride, sodium, and water in the rat. The blunting of diuretic action seen with inhibition of prostaglandin synthesis is largely, although not entirely, due to effects of indomethacin and meclofenamate on furosemide action at nephron sites proximal to the collecting duct.

Expression of peroxisomal proliferator-activated receptors and retinoid X receptors in the kidney

1999 ◽  
Vol 277 (6) ◽  
pp. F966-F973 ◽  
Author(s):  
Tianxin Yang ◽  
Daniel E. Michele ◽  
John Park ◽  
Ann M. Smart ◽  
Zhiwu Lin ◽  
...  
Keyword(s):  
Collecting Duct ◽  
Peroxisome Proliferator ◽  
Peroxisome Proliferator Activated Receptor ◽  
Retinoid X Receptors ◽  
Nephron Segments ◽  
Process Formation ◽  
Nephron Segment ◽  
Altered Cell ◽  
X Receptors ◽  
Almost All

The discovery that 15-deoxy-Δ12,14-prostaglandin J2(15d-PGJ2) is a ligand for the γ-isoform of peroxisome proliferator-activated receptor (PPAR) suggests nuclear signaling by prostaglandins. Studies were undertaken to determine the nephron localization of PPAR isoforms and their heterodimer partners, retinoid X receptors (RXR), and to evaluate the function of this system in the kidney. PPARα mRNA, determined by RT-PCR, was found predominately in cortex and further localized to proximal convoluted tubule (PCT); PPARγ was abundant in renal inner medulla, localized to inner medullary collecting duct (IMCD) and renal medullary interstitial cells (RMIC); PPARβ, the ubiquitous form of PPAR, was abundant in all nephron segments examined. RXRα was localized to PCT and IMCD, whereas RXRβ was expressed in almost all nephron segments examined. mRNA expression of acyl-CoA synthase (ACS), a known PPAR target gene, was stimulated in renal cortex of rats fed with fenofibrate, but the expression was not significantly altered in either cortex or inner medulla of rats fed with troglitazone. In cultured RMIC cells, both troglitazone and 15d-PGJ2 significantly inhibited cell proliferation and dramatically altered cell shape by induction of cell process formation. We conclude that PPAR and RXR isoforms are expressed in a nephron segment-specific manner, suggesting distinct functions, with PPARα being involved in energy metabolism through regulating ACS in PCT and with PPARγ being involved in modulating RMIC growth and differentiation.

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