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PubMed1996

Immunochemical study of transforming growth factor-beta in the kidney of the rat and chicken.

Transforming growth factor-beta (TGF-beta) is a homodimeric polypeptide of 25 kDa, which regulates cell growth and differentiation and influences extracellular matrix metabolism. Using immunochemical techniques, we identified TGF-beta in the loops of Henle and the collecting and Bellini ducts of rat kidney and in the loops of Henle of chicken kidney. Furthermore, we detected two TGF-beta-immunoreactive proteins on kidney blots of the rat of 12.5 and 47 kDa, and three on chicken kidney blots of 12.5, 34, and 47 kDa. We suggest that the precursor forms of rat and chicken TGF-beta 2 or beta 3, chicken TGF-beta 4, and the mature form of all of them are expressed in the collecting and Bellini ducts of rat kidney and the loops of Henle of rat and chicken kidney.

Animals↗
PubMed1982

On the origin of alpha-glucosidase in human urine.

The recent findings that alpha-glucosidase from human kidney was identical with one component (F1) of the alpha-glucosidases found in human urine suggested the idea that this enzyme might originate in the kidneys. The present study was performed to test this idea by immunological methods. Urine alpha-glucosidase F1 was isolated in the electrophoretically homogeneous state, and the antibody prepared in rabbits was purified by affinity chromatography after the antisera were fractionally precipitated with ammonium sulfate and chromatographed on diethylamino ethyl (DEAE)-cellulose. The staining of human kidney tissue sections was performed by the indirect method, using alpha-glucosidase F1 antibody and fluorescein-conjugated anti-rabbit immunoglobulin goat sera. The proximal convoluted portion (proximal tubules) with brush border and Henle's loops (late proximal) were stained clearly. Preincubation of intact antibody with purified antigen prevented specific staining of the proximal convoluted portion and Henle's loops. In contrast, all other tissues of kidney were stained less positively or negatively. These results indicate that alpha-glucosidase F1 originates in the kidney, and that glucosidase is specifically localized in the proximal convoluted portion and Henle's loops.

Adult↗
PubMed2000

Guanylyl cyclase-C receptor mRNA distribution along the rat nephron.

Guanylin (GN) and uroguanylin (UGN) are two recently identified peptides that have been shown to affect water and electrolyte transport in both the intestine and the kidney. Mechanistically, the effects of both peptides are thought to be mediated by intracellular cGMP which results from ligand binding to a plasma membrane guanylyl cyclase-C (GC-C) receptor. To date, the specific intrarenal site(s) of GN and UGN action have not been established. To begin to address this issue, the present studies utilized semi-quantitative RT-PCR to assess the distribution of GC-C mRNA in specific microdissected segments of the rat nephron. GC-C mRNA expression was highest in the cortical collecting tubule, followed by the proximal convoluted tubule, medullary thick ascending limb and collecting tubule, and thin limbs of Henle's loop. Expression levels were significantly lower in all other segments tested, including the glomerulus. The renal tubular expression pattern for cGMP-dependent protein kinase II (cGK-II) mRNA, which is activated in response to GN/UGN-dependent cGMP accumulation, was similar to that for GC-C. Notably, both GN and UGN mRNAs were also expressed along the nephron. The highest levels of expression for both peptides were detected in the medullary collecting tubule. Lower, but comparable levels of GN and UGN expression also occurred in the cortical collecting tubule, cortical and medullary thick ascending limb, and thin limbs of Henles loop. In the proximal convoluted tubule, GN mRNA expression was also quite high, while UGN mRNA was almost undetectable. The presence of renal GC-C and cGK-II in the kidney are consistent with a proposed endocrine function for GN and UGN. In addition however, the present data suggest that intrarenally synthesized GN and UGN may also contribute to the regulation of renal tubular transport.

Animals↗
PubMed1992

Plasma vasopressin and cortical nephron function in aging rats.

The role of vasopressin and Henle's loop transport in age-related polyuria and decrease in urine osmolality was investigated in female WAG/Rij rats free of kidney disease. In these animals, urine osmolality dropped from 2000 mosmol/kg H2O to 1000-1200 mosmol/kg H2O between 10 and 30 months, and urinary volume increased in proportion. Vasopressin concentration measured in plasma withdrawn from conscious, unrestrained, chronically catheterized rats was not significantly different in 10, 20 and 30-month-old animals (mean values 2.5 +/- 0.7, 2.2 +/- 0.2 and 2.0 +/- 0.3 pg/ml (n = 8), respectively). This suggests an impaired responsiveness of old kidney to antidiuretic hormone. The possible involvement of Henle's loop in this defect was studied by micropuncture. Paired collections of tubular fluid were done in the early distal and late proximal convolutions of the same cortical nephrons. Single nephron filtration rates did not significantly differ with age. Tubular fluid osmolalities in the early distal convolution were 165 +/- 13, 178 +/- 9 and 160 +/- 11 (n = 14) mosmol/kg H2O in 10-, 20- and 30-month-old rats, indicating similar diluting capacity of the cortical thick ascending limb. The amount of sodium transported from lumen to peritubular space by Henle's loop was also unchanged with age as were water, calcium, magnesium and potassium reabsorptions. These data indicate that the age-related decrease in urine osmolality is not related to either a significant reduced vasopressin plasma concentration or an increased single glomerular filtration rate or a reduced transport capacity of Henle's loop of the cortical nephron. Rather they suggest an impaired response to vasopressin of other segments of the nephron that is, the medullary thick ascending limb of Henle's loop and/or the collecting duct.

Aging↗
PubMed1978

Magnesium handling by the papilla of the young rat.

In a recent study it was found that in Mg loaded rats, the fraction of filtered Mg (% E Mg) recovered in the bend of the loop of Henle of papilla was greater than the filtered load. However, the site of this Mg addition was unspecified and could be either the juxtamedullary proximal tubule, the pars recta, or in the papilla, the descending limb of the loop of Henle. In order to investigate the movement of Mg in the various structures of the papilla, we have studied: 1. The transport of this electrolyte along the collecting duct. 2. Its relative concentration in the loop of Henle and in the adjacent vasa recta. The experiments have been performed in hydropenic and Mg loaded rats. In the collecting duct, the inulin and Mg concentrations increase proportionally, indicating an absence of any transport of Mg along this part of this nephron. In the vasa recta of the accessible papilla, the capillary over peripheral plasma Mg ratio (C/UF Mg) in hydropenia and after Mg loading [1.88 +/- 0.15 (ES) and 2.89 +/- 0.25] were significantly lower than the corresponding TF/UF Mg in the adjacent loops of Henle (2.90 +/- 0.17 and 4.04 +/- 0.37). This finding reduces the possibilities of a Mg passive diffusion from the capillaries to the tubular lumen, unless the electrical potential of the descending limb is more negative than -5 mV. The hypothesis of an active secretion, or a passive diffusion of Mg in the deep proximal tubule, in the pars recta, or in the early non accessible descending limb constitutes the other alternative.

Animals↗
PubMed1983

Adaptation of deep and superficial nephrons to changes in dietary phosphate intake.

Dietary phosphate intake is now recognized to be a primary regulator of renal phosphate excretion. However, the nephron sites involved in the adaptation to changes in dietary phosphate are unclear. We tested the hypothesis that deep and superficial nephrons respond differently to changes in dietary phosphate by comparing fractional phosphate delivery (FDP%) from proximal tubules of both nephron populations. Because phosphate reabsorption is not detectable in the ascending loop of Henle, FDP% to the superficial early distal tubule and papillary loop of Henle reflect delivery from superficial and deep nephron proximal tubules, respectively. Micropuncture experiments were performed in 17 acutely TPTX rats fed either a low (0.07%) or a high (1.8%) phosphate diet for 4 days prior to the experiment. In low phosphate diet, fractional phosphate excretion was 0.93 +/- 0.26%. FDP% was 7.5 +/- 0.5 and 9.1 +/- 2.2% from superficial and deep nephron proximal tubules, respectively (P greater than 0.05). In high phosphate diet, fractional phosphate excretion was 29.6 +/- 5.0%. FDP% was significantly greater from superficial proximal tubules, 33.9 +/- 4.6%, compared with that from deep nephron proximal tubules, 14.0 +/- 2.7% (P less than 0.05). We conclude that significant adaptation of phosphate reabsorption in response to changes in dietary phosphate intake occurs in the superficial but not in the deep nephron proximal tubule in acutely TPTX volume-expanded rats. In addition, the presence of distal phosphate reabsorption was not evident in high phosphate diet but must occur in low phosphate diet.

Animals↗
PubMed1986

Enolase isozymes in renal tubules and renal cell carcinoma.

To elucidate the localization of enolase isozymes in renal tubules and renal cell carcinoma, an immunohistochemical study and quantitative analysis by employing the enzyme immunoassay were performed. The alpha-enolase was localized in almost all epithelial cells of renal tubules except for loops of Henle. The gamma-enolase was localized in macula densa cells and epithelial cells of loops of Henle and collecting ducts of the medulla, but not in those of proximal tubules. In renal cell carcinoma, most tumor cells possessed two enolase isozymes. From these immunohistochemical findings, it is suggested that enolases are present mainly in the alpha alpha form in epithelial cells of proximal tubules, in the gamma gamma form in those of loops of Henle, and in the two forms and/or the alpha gamma form in tumor cells of renal cell carcinoma. The levels of gamma-enolase in the normal cortex were 16.8 +/- 3.7 ng/mg protein (n = 7), whereas those in renal cell carcinoma were 928 +/- 554 ng/mg protein (n = 7), about 55-fold higher than those in the normal cortex. The serum gamma-enolase levels were also enhanced in 20 (49%) of 41 patients with renal cell carcinoma. Because it is generally accepted that renal cell carcinoma is derived from epithelium of proximal tubules, the expression of gamma-enolase has occurred during carcinogenesis.

Carcinoma, Renal Cell↗
PubMed1998

Differential distribution of actin and cytokeratin in isolated full-length rabbit renal tubules.

The distribution of basal actin bundles and cytokeratin intermediate filaments in the rabbit kidney was examined along isolated renal tubules by confocal laser microscopy. Perfusion of collagenase and subsequent manipulation of kidney tissues yielded well preserved renal tubules free of connective tissue components often extending from glomeruli to collecting tubules. Such isolated renal tubules were fluorescently stained with phalloidin and with anti-cytokeratin antibody and then observed as whole-mount preparations by confocal laser microscopy. Epithelial cells of Bowman's capsules showed conspicuous actin bundles which were arranged parallel to each other in individual cells. In proximal ducts, thick actin bundles were seen running in the basal regions of epithelial cells perpendicular to the tubule axis. Basal actin bundles in proximal tubules appeared to be somewhat thinner and run more irregularly in more distal parts of the tubule. Thin limbs of Henle's loop showed bright but very short rod or dot-like stainings of actin, while in thick limbs, there were thick and short actin bundles. In distal tubules basal actin bundles were somewhat longer than those in thick limbs of Henle's loop. In the collecting ducts in the renal cortex, a few short actin bundles as well as dotty or patchy stainings were shown in the basal region. In both whole-mount preparations and cryostat sections, cytokeratin immunoreactivities were almost exclusively detected in epithelial cells of Henle's loops and collecting ducts but poorly in proximal and distal tubules. Epithelial cells of Henle's loops showed dense networks of cytokeratin immunoreactivities throughout the cytoplasm, whereas cell boundaries were immunostained in collecting ducts. The actin and cytokeratin distribution in such isolated renal tubules was confirmed by immunofluorescence of cryostat sections and by thin-section electron microscopy. The observations that actin and intermediate filaments varied in distribution in different segments of renal tubules are interesting in view of the segmental differentiation of renal tubule functions.

Actins↗
PubMed1986

Rat hypothalamic extract inhibits vasopressin-stimulated Na+-K+-ATPase activity in the rat renal medulla.

Arginine vasopressin stimulates Na+-K+-ATPase activity located in the rat thick ascending limb of Henle's loop. mammalian hypothalamus appears to produce a factor capable of inhibiting Na+-K+-ATPase activity in a variety of tissues. The effect of a purified rat hypothalamic extract with and without AVP on rat renal Na+-K+-ATPase activity was evaluated by a cytochemical technique. The hypothalamic extract alone failed to affect basal Na+-K+-ATPase activity throughout renal segments after 10 min exposure. Na+-K+-ATPase activity stimulated by AVP (1-10 fmol l-1) for 10 min was inhibited by rat hypothalamic extract over the concentration range 10(-7)-10(-3) U ml-1 in a dose-dependent manner. Complete inhibition of AVP-stimulated Na+-K+-ATPase activity occurred at a hypothalamic extract concentration of 10(-3) U ml-1. Only Na+-K+-ATPase activity located in the renal medullary thick ascending limb was influenced by the rat hypothalamic extract.

Animals↗
PubMedDate not supplied

Pharmacology of bumetanide.

The diuretic action of bumetanide was compared with that of furosemide following oral and intravenous administration of equipotent doses in the rat, mouse, cat, rabbit, and dog. The onset of the bumetanide-induced diuresis was rapid and lasted 4 to 6 hours. In studies of selective renal uptake, the ratio of tissue concentration to plasma concentration of bumetanide was three times greater than that of furosemide. Protein binding and metabolism studies did not reveal significant differences between the two diuretics. Bumetanide and Furosemide were excreted in dog urine as unchanged drug. Data obtained by various procedures to determine renal sites of action indicate a direct action of bumetanide at the ascending limb of Henle's loop and the proximal convoluted tubule. The altered blood flow induced by bumetanide does not per se account for the natriuretic response, but the increase in renal electrolyte excretion is thought to be linked to a prostaglandin--reninbradykinin system.

Animals↗
PubMed1987

Retention of differentiated characteristics by cultures of defined rabbit kidney epithelia.

Rabbit nephron segments of proximal convoluted tubules (PCT); proximal straight tubules (PST); cortical and medullary thick ascending limbs of Henle's loop (CAL, MAL); and cortical, outer medullary, and inner medullary collecting tubules (CCT, OMCT, IMCT) were individually microdissected and grown in monolayer culture in hormone supplemented, defined media. Factors favoring a rapid onset of proliferation included young donor age, distal tubule origin, and the addition of 3% fetal calf serum to the medium. All primary cultures had polarized morphology with apical microvilli facing the medium and basement membrane-like material adjacent to the dish. Differentiated properties characteristic of the tubular epithelium of origin retained in cultures included ultrastructural characteristics and cytochemically demonstrable marker enzyme proportions. PCT and PST were rich in alkaline phosphatase; CAL stained strongly for NaK-ATPase; CCT contained two cell populations with regard to cytochrome oxidase reaction. A CCT-specific anti-keratin antibody (aLEA) was immunolocalized in CCT cultures, and a PST cytokeratin antibody stained PST cultures. The biochemical response of adenylate cyclase to putative stimulating agents was the same in primary cultures as in freshly isolated tubules. In PCT and PST adenylate cyclase activity was stimulated by parathyroid hormone (PTH) but not by arginine vasopressin (AVP); CAL and MAL adenylate cyclase was stimulated by neither PTH nor AVP; CCT, OMCT, and IMCT adenylate cyclase was stimulated by AVP but not by PTH. NaF stimulated adenylate cyclase activity in every cultured segment. It is concluded that primary cultures of individually microdissected rabbit PCT, PST, CAL, MAL, CCT, OMCT, and IMCT retain differentiated characteristics with regard to ultrastructure, marker enzymes, cytoskeletal proteins, and hormone response of adenylate cyclase and provide a new system for studying normal and abnormal functions of the heterogeneous tubular epithelia in the kidney.

Adenylyl Cyclases↗
PubMed1998

pICln predominantly localizes at luminal surface membranes of distal tubules and Henle's ascending limbs.

We produced a highly specific antibody to the C-terminal peptide sequence of pICln. It recognized pICln with a 38-kDa molecular mass on SDS-polyacrylamide gel electrophoresis, coinciding with that previously reported. During native polyacrylamide gel electrophoresis, three immunoreactive bands (38, 70, and 130 kDa) were detected. The isoelectric point of pICln was calculated to be 4.0. Subcellular localization study showed the presence of pICln in the soluble and microsomal fraction. pICln can be easily solubilized from the membrane fraction with Triton X-100. From immunohistochemical observations, we found pICln to be obviously located on the luminal surface membranes of the distal tubules and Henle's loop ascending limbs, and it can also be found inside proximal tubular cells. The present results suggested that pICln functions as a "cytosolic anchor = membrane insertion" model, and it plays important roles in the "urine dilution segment" cells of nephrons.

Animals↗
PubMed1976

A critical reevaluation of the structure of the rat uriniferous tubule as revealed by scanning electron microscopy.

The fine structure of luminal surface of clearly identified portions of uriniferous tubules has been studied by scanning electron microscopy to elucidate some controversies concerning the topography of certain surface formations. The results show a characteristic pattern of the luminal surface in the region of Henle's loop, which was assumed by previous authors, to belong to the collecting tubule. Furthermore it is demonstrated that no cilia are present within the terminal portion of the collecting tubules.

Animals↗
PubMed1979

A functional model of the rat kidney.

A mathematical model of the nephron was developed by writing a set of material balance equations for the flow of urea, salt and water along the foregoing study and are taken here as a basis, in particular the model configuration of the collecting duct system. The stimulation of the model equatentration profiles which at the ends of the several tubular sections were consistent with the values observed in experimental investigations.e medullary interstitial solute concentration profiles are taken to increase linearly in outer and inner zone. The several transeptithelial fluxes are driven by diffusion, osmosis, solvent drag and active transport. The development of osmotic gradient in the inner medulla is taken here to be caused by active secretion of salt into the descending LImb of Henle's loop. The parameters in the flux equations for all parts of the nephron and the concentration values at the end of each tubular section are determined by collecting and averaging the values given in literature and by extrapolating the measurement data. The simulation of the model equations with these averaged parameters resulted in concentration profiles which at the ends of the several tubular sections were consistent with the values observed in experimental investigations.

Animals↗
PubMed1993

[Arginine]vasopressin hydrolyses phosphoinositides in the medullary thick ascending limb of mouse nephron.

NaCl reabsorption across the thick ascending limb of Henle's loop (TAL) is stimulated by several hormones, in particular vasopressin acting through V2 receptors and cyclic AMP production. This study used suspensions of medullary TAL (mTAL) tubules from the mouse nephron to investigate the possibility that, besides activating adenylyl cyclase, vasopressin also stimulates phospholipase C via V1 receptor occupancy. Two different methods, phosphoinositide labelling and inositol trisphosphate (InsP3) radioimmunoassay, were used to show that [arginine]vasopressin (AVP) rapidly stimulated the formation of InsP3, which peaked at 200%-250% of control within the first minute of incubation with 10 nmol/l vasopressin at 37 degrees C, and declined to basal level after 5-10 min. Dose/response curves for InsP3, established at 30 degrees C and 37 degrees C using radioimmunoassay, showed a half-maximal stimulation of InsP3 production at about 1 nmol/l AVP and a maximal response at 10 nmol/l. Similar values were obtained for the response to AVP in terms of cAMP accumulation. InsP3 content in the presence of higher concentrations of AVP (1 mumol/l) was significantly lower (P < 0.001) than in the presence of 10 nmol/l AVP, giving a bell-shaped appearance to the dose/response curve at 37 degrees C but not at 30 degrees C. The V2 receptor agonist, 1-deamino-[8-D-Arg]vasopressin (dAVP) did not stimulate the formation of InsP3, and the V1 receptor antagonist d(CH2)5[Tyr(Me)2]AVP inhibited AVP-induced InsP3 formation, which therefore appeared to be mediated by V1 receptor occupancy. Under the same conditions, AVP also induced the formation of diradylglycerol via V1 receptor activation, with an analogous dose/response curve.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Differential short-term desensitization to vasopressin, isoproterenol, glucagon, parathyroid hormone and calcitonin in the thick ascending limb of rat kidney.

Short-term desensitization to hormone-induced cAMP accumulation was investigated in the medullary (MTAL) and the cortical (CTAL) thick ascending limbs of Henle's loop isolated by microdissection from the rat kidney. The following agonists were studied: vasopressin, glucagon and human calcitonin in the MTAL, and vasopressin, glucagon, human calcitonin, parathyroid hormone (PTH) and the beta-adrenergic agonist isoproterenol in the CTAL. Isolated tubules were preincubated in vitro for 60 min in the presence or absence of a maximal concentration of one of the five agonists (vasopressin 10 nM, glucagon 10 nM, calcitonin 100 nM, PTH 10 nM, isoproterenol 1 microM). Desensitization induced by each agent to its own action was then quantified by measuring the amount of cAMP accumulating in the presence of the phosphodiesterase inhibitor isobutylmethylxanthine and the same agonist concentration as that used during preincubation. In the MTAL, as previously reported, preincubation with vasopressin led to a marked (80%-85%) desensitization to this hormone. A significant hormone self-induced desensitization of about 45% was also obtained with glucagon, but not with calcitonin. In the CTAL, the following order of potency to elicit desensitization was observed: vasopressin (80%) greater than isoproterenol (50%) greater than glucagon (30%) greater than PTH (20%, NS) greater than calcitonin (10%, NS). Thus, the magnitude of desensitization varied greatly from one hormone to another, but for a given hormone, was of roughly similar extent in both MTAL and CTAL.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Immunohistochemical localization of a protein fraction derived from rabbit renal papilla.

Studies were carried out to define antigenic characteristics of the rabbit renal collecting duct. Renal papillae of adult rabbits were homogenized, centrifuged, and the 600 X g pellet was extracted with 0.5% Triton X-100 in the presence of 1 M NaCl. The crude extract was fractionated on an anion exchange column (DEAE cellulose). A fraction enriched in acidic proteins that co-purified with a radioactive 150 kd glycoprotein from cultured collecting duct cells (Minuth 1982), was used for immunization of guinea pigs. The antiserum shows the following characteristics as revealed by indirect immunofluorescence on the rabbit kidney: 1) Among all tubular epithelial cells only principal cells of the collecting duct and the connecting tubule cell show immunoreactivity. 2) The antiserum decorates the epithelial-interstitial interface of the whole collecting duct as well as of connecting tubule and thick ascending limb of Henle's loop. 3) There is immunoreactivity of interstitial fibers throughout the kidney. 4) Epithelial cells in a variety of other organs in rabbit did not react with the antiserum. Our data demonstrate an antigenic distinction of both, the connecting tubule cell and the principal cell, discriminating these cells from other tubular epithelial cells including the intercalated cells of the collecting duct system. Furthermore, our findings point to a heterogeneity along the distal nephron with respect to the constituents of the epithelial-interstitial interface.

Animals↗
PubMed1975

A micropuncture study of the effect of isoprenaline on renal tubular fluid and electrolyte transport in the rat.

To explain the mechanism of the isoprenaline induced antidiuresis the effect of this substance on fluid and electrolyte reabsorption in various nephron segments of the rat kidney has been studied using micropuncture techniques. Isoprenaline (1.5x10-9mol/kg-min i.v.) decreased GFR of superficial nephrons and increased fractional proximal fluid, sodium and potassium reabsorption. However, the fractions of filtered fluid and electrolytes, which had been reabsorbed up to early distal tubule were unchanged after isoprenaline. This indicated that the increased fractional proximal reabsorption has been completely compensated by decreased reabsorption from Henle's loops. In the distal convoluted tubules an increase in the fractional fluid and sodium reabsorption could be established using a recollection technique. Given directly into the distal tubular lumen isoprenaline stimulated the isotonic fluid reabsorption, which was measured by the Gertz split oil droplet method. From these results it is concluded that the decrease in superficial GFR and the increased distal tubular fluid and sodium reabsorption lead to the decrease in urine volume and in urinary electrolyte excretion after isoprenaline.

Animals↗