A Combined SEM and TEM Study on the Basal Labyrinth of the Collecting Duct in the Rat Kidney.

The neonatal Fc receptor, FcRn, transports immunoglobulin G (IgG) across cellular barriers between mother and offspring. FcRn also protects circulating IgG from catabolism, probably during transport across the capillary endothelium. Only one cell culture model of transcytosis has been used extensively, the transport of IgA from the basolateral to the apical surface of Madin-Darby canine kidney cells by the polymeric immunoglobulin receptor (pIgR). We report that rat inner medullary collecting duct (IMCD) cells transfected with DNA encoding the (alpha) subunit of rat FcRn specifically and saturably transport Fc when grown as polarized monolayers. Using this system, we have found that transcytosis by FcRn, like transcytosis by the pIgR, depends upon an intact microtubule system. FcRn differs most strikingly from the pIgR in its ability to transport its ligand in both the apical to basolateral and basolateral to apical directions. The phosphatidylinositol 3-kinase inhibitors wortmannin and LY294002 inhibited basolateral to apical transport by FcRn more than apical to basolateral transport, suggesting that there are differences in the mechanisms of transport in the two directions. Lastly, we found that transcytosis by FcRn depends upon vesicular acidification. We anticipate that the IMCD cell culture model will allow further elucidation of the mechanism of IgG transport by FcRn.

Download Full-text

Urinary Reabsorption in the Rat Kidney by Anticholinergics

10.21203/rs.3.rs-199054/v1 ◽

2021 ◽

Author(s):

Hideki Oe ◽

Hatsumi Yoshiki ◽

Xinmin Zha ◽

Hisato Kobayashi ◽

Yoshitaka Aoki ◽

...

Keyword(s):

Absorption Rate ◽

Collecting Duct ◽

Rat Kidney ◽

Intracellular Camp ◽

Dependent Manner ◽

Bladder Epithelium ◽

Duct Cells ◽

Urine Production ◽

Saline Administration ◽

Collecting Duct Cells

Abstract Anticholinergics, therapeutic agents for overactive bladder, are clinically suggested to reduce urine output. We investigated whether this effect is due to bladder or kidney urine reabsorption. Various solutions were injected into the bladder of urethane-anesthetized SD rats. The absorption rate for 2 hr was examined following the intravenous administration of the anticholinergics imidafenacin (IM), atropine(AT), and tolterodine(TO). The bilateral ureter was then canulated and saline was administered to obtain a diuretic state. Anticholinergics or 1-deamino-[8-D-arginine]-vasopressin (dDAVP) were intravenously administered. After the IM and dDAVP administrations, the rat kidneys were immunostained with AQP2 antibody, and intracellular cAMP was measured. The absorption rate was ~10% of the saline injected into the bladder and constant even when anticholinergics were administered. The renal urine among peaked 2 hr after the saline administration. Each of the anticholinergics significantly suppressed the urine production in a dose-dependent manner, as did dDAVP. IM and dDAVP increased the intracellular cAMP levels and caused the AQP2 molecule to localize to the collecting duct cells' luminal side. The urinary reabsorption mechanism through the bladder epithelium was not activated by anticholinergic administration. Thus, anticholinergics suppress urine production via an increase in urine reabsorption in the kidneys' collecting duct cells via AQP2.

Download Full-text

K depletion modifies the properties of Sch-28080-sensitive K-ATPase in rat collecting duct

AJP Renal Physiology ◽

10.1152/ajprenal.1997.272.1.f124 ◽

1997 ◽

Vol 272 (1) ◽

pp. F124-F131 ◽

Cited By ~ 13

Author(s):

B. Buffin-Meyer ◽

M. Younes-Ibrahim ◽

C. Barlet-Bas ◽

L. Cheval ◽

S. Marsy ◽

...

Keyword(s):

Collecting Duct ◽

Rat Kidney ◽

Lower Sensitivity ◽

Kinetic Properties ◽

Type I ◽

Type Ii ◽

Distribution Profile ◽

Adenosine Triphosphatases ◽

Collecting Ducts ◽

K Depletion

Two distinct Sch-28080-sensitive K-adenosine triphosphatases (K-ATPases) were previously described in the rat nephron: a ouabain-resistant K-ATPase (type I) present in collecting ducts (CD) and a ouabain-sensitive from (type II) located in proximal tubules (PT) and thick ascending limbs (TAL). In K-depleted rats, K-ATPase activity is increased in CD, whereas it is reduced in PT and TAL. Because expression of colonic H-K-ATPase is restricted to the CD of K-depleted rats, we hypothesized that K-ATPase from the CD of K-depleted rats might be different from types I and II. Indeed, type III K-ATPase displays higher sensitivities to ouabain and to Sch-28080 than type II, a lower sensitivity to Sch-28080 than type I, and, conversely to types I and II, it can be stimulated by Na+. Pharmacological differences between types II and III K-ATPases were confirmed by [3H]ouabain binding experiments. Thus the rat kidney expresses three K-ATPases that differ by their pharmacological and kinetic properties, their distribution profile along the nephron and their behavior during K depletion.

Download Full-text

Urodilatin: binding properties and stimulation of cGMP generation in rat kidney cells

AJP Renal Physiology ◽

10.1152/ajprenal.1993.264.2.f267 ◽

1993 ◽

Vol 264 (2) ◽

pp. F267-F273

Author(s):

H. Saxenhofer ◽

W. R. Fitzgibbon ◽

R. V. Paul

Keyword(s):

Guanylate Cyclase ◽

Mesangial Cells ◽

Collecting Duct ◽

Rat Kidney ◽

Binding Characteristics ◽

Papillary Collecting Duct ◽

Collecting Duct Cells ◽

Medullary Collecting Duct ◽

Anp Receptors

Urodilatin (URO) [ANP-(95-126)] is an analogue of atrial natriuretic peptide (alpha-ANP) [ANP-(99-126)] that was first isolated from human urine. In rat mesangial cells, URO competed with high affinity for non-guanylate cyclase-coupled ANPR-C receptors [concentration at which 50% labeled ligand is displaced (IC50) approximately 70 pM], but with lesser affinity to the guanylate cyclase-linked ANPR-A receptors (IC50 approximately 800 pM). alpha-ANP bound to both receptors with similar affinity [dissociation constant (Kd) approximately 150 pM]. In papillary collecting duct homogenates, which possess only ANPR-A receptors, the apparent Kd value averaged 229 pM for alpha-ANP and 2.7 nM for URO. Intravenous URO was at least as potent and effective as alpha-ANP in inducing diuresis and natriuresis in anesthetized rats, but URO was approximately 10-fold less potent in stimulating guanosine 3',5'-cyclic monophosphate generation in mesangial and inner medullary collecting duct cells. We conclude that URO has a lesser affinity than alpha-ANP for guanylate cyclase-coupled ANP receptors in the kidney and that the relative natriuretic potency of URO in vivo cannot be directly attributed to its binding characteristics with ANPR-A receptors.

Download Full-text

Expression, functional analysis, and in situ hybridization of a cloned rat kidney collecting duct water channel

AJP Cell Physiology ◽

10.1152/ajpcell.1994.266.1.c189 ◽

1994 ◽

Vol 266 (1) ◽

pp. C189-C197 ◽

Cited By ~ 45

Author(s):

T. Ma ◽

H. Hasegawa ◽

W. R. Skach ◽

A. Frigeri ◽

A. S. Verkman

Keyword(s):

Base Pair ◽

Collecting Duct ◽

Rat Kidney ◽

Water Channel ◽

Cloning And Expression ◽

Base Pairs ◽

Kidney Medulla ◽

Coding Sequence ◽

Kidney Collecting Duct ◽

Protein Size

The cloning and expression of an apical membrane water channel from rat kidney collecting duct (WCH-CD) homologous to a 28-kDa integral membrane protein (CHIP28) was reported recently (K. Fushimi, S. Uchida, Y. Hara, Y. Hirata, F. Marumo, and S. Sasaki. Nature Lond. 361: 549-552, 1993). We obtained an approximately 1.8-kilobase clone from a rat kidney lambda gt10 cDNA library by a polymerase chain reaction cloning method; whereas the coding sequence (814 base pairs, predicted protein size 29 kDa) was identical to that reported, we identified an in-frame ATG codon at base pair -123 predicting a protein size of 33 kDa. On Northern blots probed by cDNAs corresponding to the WCH-CD coding sequence (base pairs +1 to +814) or 5'-untranslated sequence (-403 to -16), a single band at 1.9 kilobases was observed in kidney medulla greater than in cortex but not in other tissues; mRNA expression was increased strongly by dehydration. Translation and oocyte expression studies were performed to identify the translation start site. The short (base pairs +1 to +814) and long (base pairs -123 to +814) cDNAs were subcloned in vector pSP64 containing the 5'-untranslated Xenopus globin sequence upstream to the ATGs; a 30-base pair c-myc sequence was engineered at the COOH- terminal for antibody recognition.(ABSTRACT TRUNCATED AT 250 WORDS)

Download Full-text

AQP2 is a substrate for endogenous PP2B activity within an inner medullary AKAP-signaling complex

AJP Renal Physiology ◽

10.1152/ajprenal.2001.281.5.f958 ◽

2001 ◽

Vol 281 (5) ◽

pp. F958-F965 ◽

Cited By ~ 46

Author(s):

Inho Jo ◽

Donald T. Ward ◽

Michelle A. Baum ◽

John D. Scott ◽

Vincent M. Coghlan ◽

...

Keyword(s):

Hippocampal Neurons ◽

Collecting Duct ◽

Rat Kidney ◽

Regulatory Subunit ◽

Relative Molecular Mass ◽

Signaling Complex ◽

Anchoring Protein ◽

Pka Regulatory Subunit

We have demonstrated that inner medullary collecting duct (IMCD) heavy endosomes purified from rat kidney IMCD contain the type II protein kinase A (PKA) regulatory subunit (RII), protein phosphatase (PP)2B, PKCζ, and an RII-binding protein (relative molecular mass ∼90 kDa) representing a putative A kinase anchoring protein (AKAP). Affinity chromatography of detergent-solubilized endosomes on cAMP-agarose permits recovery of a protein complex consisting of the 90-kDa AKAP, RII, PP2B, and PKCζ. With the use of small-particle flow cytometry, RII and PKCζ were localized to an identical population of endosomes, suggesting that these proteins are components of an endosomal multiprotein complex.32P-labeled aquaporin-2 (AQP2) present in these PKA-phosphorylated endosomes was dephosphorylated in vitro by either addition of exogenous PP2B or by an endogenous endosomal phosphatase that was inhibited by the PP2B inhibitors EDTA and the cyclophilin-cyclosporin A complex. We conclude that IMCD heavy endosomes possess an AKAP multiprotein-signaling complex similar to that described previously in hippocampal neurons. This signaling complex potentially mediates the phosphorylation of AQP2 to regulate its trafficking into the IMCD apical membrane. In addition, the PP2B component of the AKAP-signaling complex could also dephosphorylate AQP2 in vivo.

Download Full-text

Production of Urea from Arginine in Pars recta and Collecting Duct of the Rat Kidney

Kidney & Blood Pressure Research ◽

10.1159/000173207 ◽

1989 ◽

Vol 12 (5-6) ◽

pp. 302-312 ◽

Cited By ~ 1

Author(s):

Olivier Levillain ◽

Annette Hus-Citharel ◽

François Morel ◽

Lise Bankir

Keyword(s):

Collecting Duct ◽

Rat Kidney ◽

Pars Recta

Download Full-text

Developmental expression of the epithelial Na+ channel in kidney and uroepithelia

AJP Renal Physiology ◽

10.1152/ajprenal.1999.276.2.f304 ◽

1999 ◽

Vol 276 (2) ◽

pp. F304-F314 ◽

Cited By ~ 12

Author(s):

Shigeru Watanabe ◽

Kazumichi Matsushita ◽

Paul B. McCray ◽

John B. Stokes

Keyword(s):

Urinary Bladder ◽

Collecting Duct ◽

Rat Kidney ◽

Rnase Protection Assay ◽

Adult Life ◽

Developmental Expression ◽

Na Channel ◽

Rnase Protection ◽

Collecting Ducts ◽

Uroepithelial Cell

The epithelial Na+ channel (ENaC) plays an important role in regulating Na+ balance in neonatal and adult life. Using in situ hybridization, we localized α-, β-, and γ-rat ENaC (rENaC) mRNA in developing rat kidney and uroepithelia. rENaC mRNA was first detectable on fetal day 16, and by fetal day 17, mRNA was abundant in the terminal collecting duct and uroepithelia. After birth, the intensity of the signals for all three subunits increased in the cortical collecting ducts and by 9 days after birth had diminished in the inner medullary collecting ducts. Expression in uroepithelial cells was different. mRNA for β- and γ-rENaC, but not α-rENaC, was detected in pelvis, ureters, and bladder at all stages of development beyond fetal day 16. By RNase protection assay (RPA), the greatest increase in subunit abundance in the kidney occurred before birth. Between postnatal days 9 and 30, the abundance of β- and γ-rENaC decreased relative to α-rENaC in outer and inner medulla. The urinary bladder, in contrast, demonstrated the greatest increase in β- and γ-rENaC mRNA abundance after birth. We were generally unable to detect α-rENaC by RPA in urinary bladder. Feeding weaned rats a diet of high or low NaCl did not change the abundance of any of the subunit mRNAs in bladder. These results demonstrate additional heterogeneity of developmental expression and regulation of ENaC. The differences between the collecting duct and uroepithelial cell rENaC mRNA regulation raise the possibility of significant differences in function.

Download Full-text

Localization and regulation of PKA-phosphorylated AQP2 in response to V2-receptor agonist/antagonist treatment

AJP Renal Physiology ◽

10.1152/ajprenal.2000.278.1.f29 ◽

2000 ◽

Vol 278 (1) ◽

pp. F29-F42 ◽

Cited By ~ 135

Author(s):

Birgitte Mønster Christensen ◽

Marina Zelenina ◽

Anita Aperia ◽

Søren Nielsen

Keyword(s):

Plasma Membrane ◽

Immunoelectron Microscopy ◽

Collecting Duct ◽

Rat Kidney ◽

Fold Increase ◽

Apical Plasma Membrane ◽

Complete Disappearance ◽

Vasopressin Secretion ◽

V2 Receptor ◽

Intracellular Vesicles

Phosphorylation of Ser256, in a PKA consensus site, in AQP2 (p-AQP2) appears to be critically involved in the vasopressin-induced trafficking of AQP2. In the present study, affinity-purified antibodies that selectively recognize AQP2 phosphorylated at Ser256 were developed. These antibodies were used to determine 1) the subcellular localization of p-AQP2 in rat kidney and 2) changes in distribution and/or levels of p-AQP2 in response to [desamino-Cys1,d-Arg8]vasopressin (DDAVP) treatment or V2-receptor blockade. Immunoelectron microscopy revealed that p-AQP2 was localized in both the apical plasma membrane and in intracellular vesicles of collecting duct principal cells. Treatment of rats with V2-receptor antagonist for 30 min resulted in almost complete disappearance of p-AQP2 labeling of the apical plasma membrane with only marginal labeling of intracellular vesicles remaining. Immunoblotting confirmed a marked decrease in p-AQP2 levels. In control Brattleboro rats (BB), lacking vasopressin secretion, p-AQP2 labeling was almost exclusively present in intracellular vesicles. Treatment of BB rats with DDAVP for 2 h induced a 10-fold increase in p-AQP2 labeling of the apical plasma membrane. The overall abundance of p-AQP2, however, was not increased, as determined both by immunoelectron microscopy and immunoblotting. Consistent with this, 2 h of DDAVP treatment of normal rats also resulted in unchanged p-AQP2 levels. Thus the results demonstrate that AQP2 phosphorylated in Ser256 is present in the apical plasma membrane and in intracellular vesicles and that both the intracellular distribution/trafficking, as well as the abundance of p-AQP2, are regulated via V2 receptors by altering phosphorylation and/or dephosphorylation of Ser256in AQP2.

Download Full-text