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1.
Am J Kidney Dis ; 38(4): 777-84, 2001 Oct.
Article in English | MEDLINE | ID: mdl-11576881

ABSTRACT

Autosomal dominant polycystic kidney disease (ADPKD) accounts for 8% to 10% of patients with end-stage renal disease (ESRD) in the United States and Europe. Progressive expansion of multiple bilateral renal cysts leads to massive enlargement of the kidneys and progressive renal failure. Extrarenal manifestations of ADPKD, such as liver cysts, intracranial aneurysms, cardiac valvular disease, and perhaps diverticulosis, have been documented extensively in cross-sectional studies, but little is known about their natural history. It is thought that extrarenal aspects of ADPKD contribute to increased mortality, yet survival on dialysis of the ADPKD population surpasses that of the general dialysis population. To address this issue, we analyzed the relative risk and causes of death after ESRD in ADPKD versus nondiabetic controls using data from the United States Renal Data System. Relative risk of death from any cause, including the major extrarenal manifestations of ADPKD, was determined as a function of ESRD treatment modality (dialysis or transplantation). We found a lower total mortality rate in ADPKD ESRD patients compared with nondiabetic control ESRD patients (relative risk of death in ADPKD = 0.57; P < 0.001). Mortality rates of extrarenal complications except for polycystic liver disease were similar or lower in ADPKD patients than in nondiabetic controls. Mortality secondary to extrarenal complications was substantially lower than that secondary to cardiovascular or cerebrovascular disease.


Subject(s)
Kidney Failure, Chronic/mortality , Polycystic Kidney Diseases/mortality , Adult , Case-Control Studies , Cause of Death , Cerebrovascular Disorders/mortality , Cysts/mortality , Humans , Kidney Failure, Chronic/etiology , Kidney Failure, Chronic/therapy , Kidney Transplantation/mortality , Liver Diseases/mortality , Polycystic Kidney Diseases/genetics , Polycystic Kidney Diseases/therapy , Proportional Hazards Models , Renal Dialysis/mortality , Risk , Survival Analysis
4.
Am J Physiol ; 272(5 Pt 1): C1748-56, 1997 May.
Article in English | MEDLINE | ID: mdl-9176168

ABSTRACT

Liver cysts, the most common extrarenal manifestation of autosomal dominant polycystic kidney disease (ADPKD), derive from the intrahepatic biliary epithelium (IBE) and are found in 60-75% of ADPKD patients on dialysis. Secretin-induced secretion by the normal IBE is rich in HCO3-, whereas intact ADPKD liver cysts secrete primarily Cl- in response to secretin. To evaluate the mechanisms of decreased HCO3- secretion by ADPKD liver cysts, we utilized SV40 large T antigen-immortalized normal IBE and ADPKD liver cyst-derived epithelia (LCDE) cell lines that we created. These cell lines express biliary but not hepatocyte markers. Anion exchanger (AE) function was assessed by the response of intracellular pH (pHi) to acute Cl- removal. 2',7'-Bis(carboxyethyl)-5-(6)-carboxyfluorescein-loaded monolayers were continuously perfused with physiological HCO3- buffer containing Cl- or gluconate. In IBE cell line H75 (n = 6), acute Cl- removal alkalinized pHi at a rate of 0.04 +/- 0.01 min-1. AE function was significantly decreased in LCDE cell line CL3 (n = 6) to a rate of 0.01 +/- 0.01 min-1 after Cl- removal. Northern blot analysis demonstrated equivalent levels of AE2 mRNA in both cell lines. AE1 mRNA was undetectable. Immunoblot analysis demonstrated the AE2 polypeptide in both cell lines, but the level of mature glycosylated AE2 polypeptide was reduced in LCDE cells. Immunofluorescence microscopy demonstrated decreased membrane-localized AE2 in LCDE cells. These findings suggest that decreased plasmalemmal AE2 may account for decreased AE function in LCDE cells and suggest a possible explanation for decreased secretion of HCO3- by ADPKD liver cysts.


Subject(s)
Antiporters/metabolism , Polycystic Kidney, Autosomal Dominant/metabolism , Alkalies/pharmacology , Bile Ducts, Intrahepatic/cytology , Bile Ducts, Intrahepatic/metabolism , Blotting, Western , Buffers , Cell Line, Transformed , Chloride-Bicarbonate Antiporters , Chlorides/metabolism , Cysts/metabolism , Cysts/pathology , Fluorescent Antibody Technique, Indirect , Humans , Hydrogen-Ion Concentration , Intracellular Membranes/metabolism , Liver Diseases/metabolism , Liver Diseases/pathology , Polycystic Kidney, Autosomal Dominant/pathology , Reference Values , Tetradecanoylphorbol Acetate/pharmacology , Tissue Distribution
5.
Connect Tissue Res ; 33(4): 249-56, 1996.
Article in English | MEDLINE | ID: mdl-8834442

ABSTRACT

Hepatic cysts derived from intrahepatic bile ducts are the most common extrarenal manifestation of autosomal dominant polycystic kidney disease (ADPKD). Cyst enlargement involves cell proliferation, fluid secretion into cysts, and alterations in extracellular matrix. To study hepatic cyst formation, continuous cell lines from human normal intrahepatic biliary epithelium (IBE) and ADPKD liver cyst-derived epithelium (LCDE) were developed. Because matrix degradation and remodeling are important for cyst formation and growth, we investigated matrix modifying enzymes expressed in IBE and LCDE cell lines. Gelatin substrate zymography showed that two matrix degrading activities with characteristics of matrix metalloproteinases are secreted from these cell lines. Western immunoblotting suggests that these activities correspond to the 72 kDa (Gelatinase A) and 92 kDa (Gelatinase B) type IV collagenases. Although the level of Gelatinase A activity is comparable in both IBE and LCDE cell lines, Gelatinase B activity is substantially increased in LCDE lines.


Subject(s)
Bile Ducts, Intrahepatic/enzymology , Extracellular Matrix/enzymology , Liver/enzymology , Metalloendopeptidases/metabolism , Polycystic Kidney, Autosomal Dominant/enzymology , 3T3 Cells , Animals , Bile Ducts, Intrahepatic/cytology , Cell Line , Epithelial Cells , Gelatin/metabolism , Humans , Immunoblotting , Liver/cytology , Mice
6.
Am J Physiol ; 270(1 Pt 2): F148-53, 1996 Jan.
Article in English | MEDLINE | ID: mdl-8769833

ABSTRACT

We have produced a continuous cell line using retroviral transduction of simian virus 40 (SV40) large T antigen into epithelial cells grown from a cystoscopic bladder biopsy from a female patient with interstitial cystitis. Immortalized urothelial cells are grown in a hormonally supplemented medium in the presence of lethally irradiated NIH-3T3 fibroblast coculture. They maintain their epithelial appearance and are positive for cytokeratins. SV40 large T antigen is localized to the cell nucleus. When grown on Anocell permeable supports, the cells form a complex epithelium with scalloped luminal membranes, apical junctional complexes containing tight junctions, stratification, transepithelial resistance of 500-1,000 omega.cm2, amiloride-sensitive short-circuit current indicative of active transepithelial Na+ absorption, and functional evidence for basolateral Na-K-adenosinetriphosphatase. This immortalized bladder cell line will facilitate the study of human bladder epithelial function and the response to diverse physiological and pathophysiological stimuli.


Subject(s)
Amiloride/pharmacology , Cell Line, Transformed , Sodium/metabolism , Urinary Bladder/cytology , Urinary Bladder/metabolism , Absorption/drug effects , Antigens, Polyomavirus Transforming/genetics , Electric Conductivity , Female , Humans , Microscopy, Electron , Retroviridae/genetics , Sodium-Potassium-Exchanging ATPase/physiology , Transduction, Genetic , Urinary Bladder/drug effects
7.
Am J Physiol ; 269(3 Pt 1): G335-45, 1995 Sep.
Article in English | MEDLINE | ID: mdl-7573443

ABSTRACT

We have produced continuous cell lines using retroviral transduction of SV40 large T antigen into epithelial cells removed from the lumen of liver cysts from four female patients with autosomal dominant polycystic kidney disease (ADPKD). Liver cyst-derived epithelial (LCDE) cell lines are grown in a hormonally supplemented medium in the presence of lethally irradiated NIH/3T3 fibroblast coculture. LCDE cells maintain their epithelial appearance and are positive for the biliary-specific markers cytokeratin 7 and 19 and gamma-glutamyl transpeptidase while being negative for hepatocyte markers. SV40 large T antigen is localized to the cell nucleus. LCDE cells have been grown continuously for periods exceeding 12 mo and 25 passages (170 population doublings). LCDE cells exhibit intracellular pH regulatory pathways that, with one exception, are similar to those found in normal intrahepatic biliary epithelium. These LCDE cell lines exhibit impaired alkalinization in response to Cl- substitution. This finding is suggestive of decreased function or abundance of a Cl-/HCO3- anion exchanger and could account for the failure of ADPKD hepatic cysts to secrete HCO3- in response to secretin.


Subject(s)
Bile Ducts, Intrahepatic/pathology , Liver/pathology , Polycystic Kidney, Autosomal Dominant/pathology , 3T3 Cells , Animals , Antigens, Polyomavirus Transforming/metabolism , Bile Ducts, Intrahepatic/metabolism , Cell Line, Transformed , Cell Transformation, Viral , Cells, Cultured , Coculture Techniques , Epithelium/metabolism , Epithelium/pathology , Female , Humans , Hydrogen-Ion Concentration , Liver/metabolism , Mice , Polycystic Kidney, Autosomal Dominant/metabolism , Retroviridae/physiology
8.
Cell Calcium ; 17(5): 375-83, 1995 May.
Article in English | MEDLINE | ID: mdl-7553790

ABSTRACT

The mechanisms that regulate ion and fluid transport by the human intrahepatic bile duct have not been well defined. Human intrahepatic biliary cell lines that we have developed were used to identify and characterize purinoceptors based on increases in intracellular calcium in response to ATP and other nucleotides. Intracellular free calcium was measured in cell suspensions using the fluorescent probe Fura-2 and a fluorescence spectrophotometer. Halide efflux was measured in single cells using fluorescence microscopy and the fluorescent probe SPQ. Intracellular calcium increases equivalently in response to ATP and UTP, peaking, then diminishing to a new, elevated baseline. The peak elevation of calcium is the result of both the release of intracellular stores of calcium and the influx of extracellular calcium. The purinoceptor P2U-subtype was identified based on the potency rank order of ATP-analogues. Halide efflux increases with P2U-purinoceptor stimulation which is consistent with the opening of a Ca(2+)-sensitive Cl- channel. The physiological significance of P2U-purinoceptor activation and its effect on the ionic content and flow rate of bile remains to be determined.


Subject(s)
Bile Ducts, Intrahepatic/metabolism , Calcium/metabolism , Chloride Channels/metabolism , Receptors, Purinergic P2/physiology , Adenosine Triphosphate/analogs & derivatives , Adenosine Triphosphate/metabolism , Adenosine Triphosphate/pharmacology , Bile Ducts, Intrahepatic/cytology , Biological Transport , Calcium/pharmacology , Cell Line , Dose-Response Relationship, Drug , Epithelial Cells , Fura-2 , Humans , Ionomycin/pharmacology , Organelles/metabolism , Receptors, Purinergic P2/biosynthesis , Spectrometry, Fluorescence , Uridine Triphosphate/metabolism , Uridine Triphosphate/pharmacology
9.
Am J Physiol ; 268(3 Pt 2): F398, 1995 Mar.
Article in English | MEDLINE | ID: mdl-7535000

ABSTRACT

Cyst enlargement in autosomal dominant polycystic kidney disease (ADPKD) results in part from the transport of solute and fluid into the lumen of the cyst. In proximal tubules and thin descending limbs of normal kidneys, the high transepithelial water permeability of these segments is due to the presence of the water channel protein, aquaporin-CHIP (AQP-CHIP, i.e., AQP-1). The collecting ducts of normal kidneys express another member of this gene family, the aquaporin collecting duct (AQP-CD, i.e., AQP-2). The expression and distribution of these two members of the aquaporin gene family were examined in ADPKD and normal human kidneys. In both tissues, Western blotting with the anti-AQP-CHIP antibody revealed a major 28-kDa band. By immunofluorescence, AQP-CHIP was present in proximal tubules and thin descending limbs of Henle of both normal and ADPKD kidneys. In the latter, AQP-CHIP was detected in the epithelia lining 71% of cysts. Many cysts were positive for the proximal tubule marker gp330 (44%). Some cysts expressing AQP-CHIP did not stain for gp330, suggesting a descending thin limb origin, and a few cysts were negative for both markers. In normal human kidney, Western blotting with the anti-AQP-CD antibody revealed a band at 28 kDa. AQP-CD was localized to collecting ducts and did not show colocalization with gp330 in normal human kidney. In ADPKD kidney, AQP-CD was expressed by only 8% of cysts. In summary, water channels, primarily AQP-CHIP, are expressed in epithelial cells lining cysts in approximately 80% of cysts in ADPKD kidneys.(ABSTRACT TRUNCATED AT 250 WORDS)


Subject(s)
Aquaporins , Ion Channels/metabolism , Kidney/metabolism , Polycystic Kidney, Autosomal Dominant/metabolism , Amino Acid Sequence , Aquaporin 1 , Aquaporin 2 , Aquaporin 6 , Biological Transport, Active , Biomarkers , Blood Group Antigens , Fluorescent Antibody Technique , Humans , In Vitro Techniques , Ion Channels/genetics , Kidney/pathology , Kidney Tubules, Proximal/metabolism , Loop of Henle/metabolism , Molecular Sequence Data , Peptides/genetics , Peptides/metabolism , Polycystic Kidney, Autosomal Dominant/etiology , Polycystic Kidney, Autosomal Dominant/pathology , Water/metabolism
10.
Gastroenterology ; 108(2): 584-92, 1995 Feb.
Article in English | MEDLINE | ID: mdl-7530672

ABSTRACT

BACKGROUND/AIMS: Hepatobiliary disease is the second most common cause of mortality in patients with cystic fibrosis (CF). In the liver, only the intrahepatic biliary epithelial (IBE) cells express cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel. The aim of this study was to determine whether human CF-derived IBE cells can be infected with adenovirus and the CF phenotype complemented. METHODS: IBE cells were isolated from 2 patients with CF and immortalized using retrovirus transduction of SV40 large T antigen. Immortalized cells were infected with the adenovirus vector Ad2/CFTR2 and assayed 2-31 days postinfection for cyclic adenosine monophosphate (cAMP)-induced halide efflux. Halide efflux was measured in single cells using fluorescence microscopy and the fluorescent probe 6-methoxy-N-(3-sulfopropyl)-quinolinium. RESULTS: CF-derived IBE cell lines express biliary specific markers and express no cAMP-inducible halide efflux. Following infection with the adenovirus vector Ad2/CFTR2, a cAMP-induced halide efflux was observed for 31 days, although the number of responsive cells decreased with time. CONCLUSIONS: Human CF-IBE cells can be infected by adenovirus and the defective CFTR complemented. The loss of responsive cells with time could be due to loss of construct and/or a reduced growth of cells that are overexpressing CFTR. These CF-IBE cell lines offer an opportunity to determine the mechanisms responsible for hepatobiliary disease in the patients with CF.


Subject(s)
Bile Ducts/metabolism , Cystic Fibrosis/therapy , Genetic Therapy , Membrane Proteins/genetics , 3T3 Cells , Animals , Cell Line , Cystic Fibrosis Transmembrane Conductance Regulator , Epithelium , Genetic Complementation Test , Genetic Vectors , Humans , Mice , Transfection
11.
Am J Public Health ; 84(8): 1299-303, 1994 Aug.
Article in English | MEDLINE | ID: mdl-8059889

ABSTRACT

OBJECTIVES: The purpose of this study was to determine whether diet adversely affected survival among 2572 older persons with indicators of kidney disease in a population-based cohort. Average follow-up time for survivors, of whom 1453 (57%) had died at analysis, was 14.5 years. METHODS: Kidney disease indicators were a "yes" response to "Has a doctor ever told you that you have kidney disease or renal stones?" and/or trace or greater amounts of protein in urine. Dietary protein intakes were calculated from 24-hour recalls. RESULTS: Cox proportional hazards models were used, stratified by sex, with age, body mass index, blood pressure, education, smoking status, total caloric intake, and diabetes mellitus as covariates. Relative risk of total mortality with an additional 15 g of protein per day was 1.25 (95% confidence interval [CI] = 1.09, 1.42) among White men with kidney disease indicators, vs 1.00 (95% CI = 0.95, 1.06) among those without them; relative risks of renal-related mortality were 1.32 (95% CI = 0.97, 1.79) and 0.95 (95% CI = 0.81, 1.11), respectively. No significant differences were found for White women. CONCLUSIONS: Once chronic renal disease is present, diet may be associated with earlier mortality in White males.


Subject(s)
Dietary Proteins/administration & dosage , Kidney Diseases/diet therapy , Kidney Diseases/mortality , Population Surveillance , Age Factors , Aged , Cause of Death , Confidence Intervals , Diet Surveys , Female , Follow-Up Studies , Humans , Male , Proportional Hazards Models , Risk Factors , Sex Factors , Survival Rate , United States/epidemiology
12.
J Am Soc Nephrol ; 5(1): 27-35, 1994 Jul.
Article in English | MEDLINE | ID: mdl-7948781

ABSTRACT

The decreased abundance and enzymatic activity of myocardial Na,K-ATPase have been recognized previously to occur in chronic uremia. However, the activity of the cardiac sodium pump as defined by the uptake of 86Rb is normal. The discrepancies between these findings may have resulted from the inability to distinguish between the different Na,K-ATPase isoforms now known to exist in cardiac muscle. To investigate this question, steady-state levels of Na,K-ATPase alpha and beta mRNA isoforms, alpha 1, alpha 2, and beta 1 protein, and specific high-affinity binding of [3H]ouabain were quantitated in cardiac muscle from uremic and pair-fed, sham-operated control rats. Steady-state levels of alpha 2 and beta 2 mRNA were significantly decreased (percentage of control levels: alpha 2, 48 +/- 10; beta 2, 74 +/- 9; N = 10; P < 0.025) in chronic renal failure without any change in alpha 1, alpha 3, or beta 1 expression. The number of high-affinity [3H]ouabain-binding sites and Na,K-ATPase alpha 1, alpha 2, and beta 1 subunits was not different from control. In acute renal failure, alpha 2 and beta 2 mRNA levels also were significantly decreased (percentage of control levels: alpha 2, 24 +/- 5; beta 2, 44 +/- 8; N = 6; P < 0.001), but there was no change in the level of alpha 3 or beta 1 mRNA, the number of high-affinity [3H]ouabain-binding sites, or the level of Na,K-ATPase alpha 2 and beta 1 subunits.(ABSTRACT TRUNCATED AT 250 WORDS)


Subject(s)
Gene Expression Regulation, Enzymologic , Isoenzymes/biosynthesis , Muscle Proteins/biosynthesis , Myocardium/enzymology , Sodium-Potassium-Exchanging ATPase/biosynthesis , Uremia/enzymology , Acute Kidney Injury/complications , Animals , Antihypertensive Agents/therapeutic use , Blotting, Northern , Blotting, Western , Hypertension, Renal/drug therapy , Hypertension, Renal/enzymology , Isoenzymes/genetics , Kidney Failure, Chronic/complications , Male , Muscle Proteins/genetics , Muscles/enzymology , Ouabain/pharmacology , RNA, Messenger/biosynthesis , Rats , Rats, Sprague-Dawley , Rubidium , Sodium-Potassium-Exchanging ATPase/genetics , Uremia/etiology
13.
Am J Physiol ; 266(6 Pt 1): G1060-70, 1994 Jun.
Article in English | MEDLINE | ID: mdl-8023938

ABSTRACT

We have produced continuous cell lines using retroviral transduction of SV40 large T antigen into human intrahepatic biliary epithelial (IBE) cells from three different normal individuals. These IBE cell lines grow in a hormone-supplemented medium in the presence of NIH/3T3 fibroblast coculture. These cells maintain their epithelial appearance and are positive for the biliary-specific markers cytokeratins 7 and 19 and gamma-glutamyl transpeptidase while being negative for the hepatocyte markers albumin and asialoglycoprotein receptor. To evaluate ion transport pathways in IBE cell lines, we utilized intracellular pH (pHi) measurements obtained using the intracellular fluorescent indicator 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein. In the absence of HCO3(-)-CO2, an amiloride-sensitive Na(+)-H+ exchanger participated in the regulation of basal pHi. In the presence of HCO3(-)-CO2, a 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS)-sensitive, Na-, Cl-, and HCO3(-)-dependent acid extrusion mechanism accounted for approximately 60% of pHi recovery from acidic pHi; this mechanism is most consistent with the presence of a Na-dependent Cl-HCO3- exchanger (Na+HCO3(-)-Cl-H+). Under basal conditions, Cl- depletion revealed a DIDS-sensitive alkalinization consistent with a Na-independent Cl(-)-HCO3- exchanger. These model systems will allow the opportunity to study the normal mechanisms of IBE function and to study the pathobiology of IBE processes in disease states.


Subject(s)
Bile Ducts, Intrahepatic/metabolism , Hydrogen-Ion Concentration , Intracellular Membranes/metabolism , 3T3 Cells , Animals , Antiporters/metabolism , Bicarbonates/pharmacology , Bile Ducts, Intrahepatic/cytology , Blotting, Northern , Cell Line, Transformed , Chloride-Bicarbonate Antiporters , Culture Media , Epithelial Cells , Epithelium/metabolism , Humans , Mice
14.
Clin Chem ; 38(10): 1933-53, 1992 Oct.
Article in English | MEDLINE | ID: mdl-1394976

ABSTRACT

The serum creatinine concentration is widely interpreted as a measure of the glomerular filtration rate (GFR) and is used as an index of renal function in clinical practice. Glomerular filtration of creatinine, however, is only one of the variables that determines its concentration in serum. Alterations in renal handling and metabolism of creatinine and methodological interferences in its measurement may have a profound impact on the serum concentration of creatinine. We review the fundamental principles of physiology, metabolism, and analytical chemistry that are necessary to correctly interpret the serum creatinine concentration. These principles are then applied to important clinical circumstances, including aging, pregnancy, diabetes mellitus, drug administration, and acute and chronic renal failure. Despite numerous limitations, serum creatinine remains a useful clinical tool, but more accurate measures of renal function are frequently necessary.


Subject(s)
Creatinine/blood , Kidney Diseases/physiopathology , Kidney/physiopathology , Aging/physiology , Creatinine/urine , Diabetes Mellitus/physiopathology , Female , Glomerular Filtration Rate , Humans , Male
16.
Am J Physiol ; 260(2 Pt 2): F204-9, 1991 Feb.
Article in English | MEDLINE | ID: mdl-1996672

ABSTRACT

Recent evidence indicates the existence of a protein related to the erythroid chloride-bicarbonate exchanger (band 3 protein) in the basolateral aspect of type A intercalated cells of the distal nephron. To probe the possible participation of this transporter in the renal adaptation to chronic hypercapnia, we examined the steady-state abundance of band 3 mRNA in the kidney during respiratory acidosis of variable duration. Total RNA was isolated from renal cortex and medulla of rats maintained in a 10% CO2 atmosphere for 2 or 5 days and from contemporaneous controls. The RNA was analyzed by Northern blot assay using cDNA probes for band 3 and beta-actin genes. Using a 3' cDNA probe encoding the membrane-associated domain of band 3 protein that is involved in anion exchange, we found a two- to threefold increase in steady-state mRNA levels (whether or not correction for the beta-actin signals was applied) in renal cortex and medulla at 5 days of hypercapnia. Similar, but less definitive, increases were observed at the 2-day time point. Using a 5' cDNA probe encoding an erythroid-protein segment absent from the kidney band 3 major transcript, we detected meager hybridization in renal tissue and no measurable variation during hypercapnia. Use of splenic RNA as a positive control for the 5' probe disclosed marked reduction of band 3 mRNA levels in hypercapnia, indicating organ specificity of band 3 gene expression. We conclude that steady-state levels of kidney band 3 mRNA increase in chronic respiratory acidosis as a result of transcriptional or posttranscriptional regulatory mechanisms. This adaptation might be involved in the augmentation of renal acidification characteristic of chronic hypercapnia.


Subject(s)
Acidosis, Respiratory/metabolism , Anion Exchange Protein 1, Erythrocyte/genetics , Kidney/metabolism , RNA, Messenger/metabolism , Animals , Chronic Disease , Hypercapnia/metabolism , Kidney Cortex/metabolism , Kidney Medulla/metabolism , Male , Rats , Rats, Inbred Strains , Spleen/metabolism , Transcription, Genetic
17.
Am J Kidney Dis ; 16(3): 224-35, 1990 Sep.
Article in English | MEDLINE | ID: mdl-2205098

ABSTRACT

Assessment of glomerular filtration rate (GFR) with inulin is cumbersome and time-consuming. Radioisotopic filtration markers have been studied as filtration markers because they can be used without continuous intravenous (IV) infusion and because analysis is relatively simple. Although the clearances of 99mTc-diethylenetriamine-pentaacetic acid (DTPA), 169Yb-DTPA, and 125I-iothalamate have each been compared with inulin, rarely has the comparability of radioisotopic filtration markers been directly evaluated in the same subject. To this purpose, we determined the renal clearance of inulin administered by continuous infusion and the above radioisotopic filtration markers administered as bolus injections, simultaneously in four subjects with normal renal function and 16 subjects with renal insufficiency. Subjects were studied twice in order to assess within-study and between-study variability. Unlabeled iothalamate was infused during the second half of each study to assess its effect on clearances. We found that renal clearance of 125I-iothalamate and 169Yb-DTPA significantly exceeded clearance of inulin in patients with renal insufficiency, but only by several mL.min-1.1.73m-2. Overestimation of inulin clearance by radioisotopic filtration markers was found in all normal subjects. No differences between markers were found in the coefficient of variation of clearances either between periods on a given study day (within-day variability) or between the two study days (between-day variability). The true test variability between days did not correlate with within-test variability. We conclude that the renal clearance of 99mTc-DTPA, 169Yb-DTPA, or 125I-iothalamate administered as a single IV or subcutaneous injection can be used to accurately measure GFR in subjects with renal insufficiency; use of the single injection technique may overestimate GFR in normal subjects.


Subject(s)
Glomerular Filtration Rate , Kidney Failure, Chronic/physiopathology , Radioisotopes , Creatinine/urine , Female , Humans , Inulin , Iodine Radioisotopes , Iothalamic Acid , Kidney Failure, Chronic/urine , Male , Metabolic Clearance Rate , Middle Aged , Organotechnetium Compounds , Pentetic Acid , Technetium Tc 99m Pentetate , Urea/urine , Ytterbium
18.
Pflugers Arch ; 416(6): 632-8, 1990 Aug.
Article in English | MEDLINE | ID: mdl-2123337

ABSTRACT

We have previously demonstrated that, in the absence of Na+ in vitro, the rate of colonic K+ absorption is increased by increasing PCO2. Chronic secondary hyperaldosteronism induced by dietary Na-depletion further stimulated K+ absorption under these conditions. Because the observed increments in CO2-dependent K+ absorption were not accompanied by corresponding changes in short-circuit current, macroscopic electroneutrality must have been maintained either by anion absorption or by cation secretion. Colonic Cl- absorption is known to respond to increased PCO2 both in vivo and in vitro, but its response under Na-free conditions and the relationship to K+ absorption have not been examined. To determine the relationship of Cl- absorption to K+, we measured unidirectional fluxes of 36Cl and the response to PCO2 in voltage-clamped segments of rat distal colon. Our findings indicate that the rate of Cl- absorption is increased by increasing CO2, both in the presence and absence of Na+. Under Na-free conditions, Cl- absorption is inhibited by acetazolamide and by the absence of K+;K+ absorption (86Rb or 42K flux) is inhibited in a reciprocal fashion by the absence of Cl-. The rates of K+ and Cl- absorption are similar in controls and after secondary hyperaldosteronism due to a Na-deficient diet. These findings suggest that K- and Cl- absorption are closely coupled under Na-free conditions, most likely due to the operation of parallel, aldosterone-responsive H(+)-K+ and Cl(-)-HCO3- exchange pathways.


Subject(s)
Aldosterone/pharmacology , Carbon Dioxide/pharmacology , Chlorides/pharmacology , Colon/metabolism , Potassium/pharmacology , Acetazolamide/pharmacology , Animals , Colon/physiology , Rats , Sodium/physiology
19.
Pflugers Arch ; 416(6): 639-45, 1990 Aug.
Article in English | MEDLINE | ID: mdl-2174145

ABSTRACT

Recent studies from this laboratory have determined that colonic K+ absorption is altered by the PCO2 and by secondary hyperaldosteronism. Partial inhibition by vanadate and mucosal ouabain suggested the operation of an H+/K+ exchange pump. To determine the mechanism of acidification in rat distal colon, we measured in vitro acidification using the pH-stat technique by voltage-clamped segments of colonic epithelium in controls and in the presence of secondary hyperaldosteronism, induced by a sodium-deficient diet. Chronic stimulation with aldosterone resulted in increased mucosal acidification in vitro for at least 2 h. This effect could not be accounted for by lactate production and was not altered by elimination of the aldosterone-induced increase in voltage and short-circuit current with 10 microM amiloride. Studies with inhibitors and ion substitution revealed that mucosal acidification resulted from both Na-dependent and Na-independent mechanisms. Na-dependent acidification was inhibited by ATPase inhibitors and was mediated in part by a luminal Na+/H+ exchanger in the presence of secondary hyperaldosteronism. Na-independent acidification was mediated by a pathway dependent on luminal K+ that was inhibited by vanadate and mucosal ouabain, consistent with the operation of an H+/K+ exchange pump.


Subject(s)
Colon/physiopathology , Hyperaldosteronism/physiopathology , Adenosine Triphosphatases/antagonists & inhibitors , Amiloride/pharmacology , Animals , Carrier Proteins/physiology , Colon/metabolism , Colon/ultrastructure , Diet/adverse effects , Electric Stimulation , Hydrogen/metabolism , Hydrogen-Ion Concentration , Hyperaldosteronism/etiology , Hyperaldosteronism/metabolism , Lactates/metabolism , Lactic Acid , Male , Membrane Potentials/physiology , Ouabain/pharmacology , Rats , Rats, Inbred Strains , Sodium/deficiency , Sodium/physiology , Sodium-Hydrogen Exchangers , Vanadates/pharmacology
20.
Am J Physiol ; 259(1 Pt 2): F65-71, 1990 Jul.
Article in English | MEDLINE | ID: mdl-2115740

ABSTRACT

Mineralocorticoid steroids markedly alter ion transport in responsive epithelia. Increases in absorption of Na+ and secretion of K+ and H+ are accompanied by increases in surface area of the basolateral membrane. The basolateral membrane changes are associated with increased Na(+)-K(+)-ATPase activity and increased numbers of Na(+)-K(+)-ATPase pump sites. It is thought that H+ secretion is mediated by H+ pumps contained in apical vesicles that are added to the luminal membrane in response to acidifying stimuli. Whether there are changes in the number or volume of apical vesicles in response to aldosterone has not been evaluated. To this purpose, we evaluated apical membrane morphology in rat distal colon, a mineralocorticoid-responsive epithelium. We found that aldosterone infused for 4-7 days by osmotic minipump significantly increased the number, surface density, and total volume of apical vesicles. Exposure of tissues to 5% CO2 for 15 min before fixation resulted in significant decreases in vesicle number, surface density, and volume in aldosterone-stimulated tissues. After CO2, apical vesicles in aldosterone-stimulated tissues tended to be closer to the luminal membrane; apical membrane surface density was increased but not to a significant degree. Fluorescence microscopy demonstrated acridine orange accumulation in discrete points under the lumen, suggesting the presence of acidic vesicles in this location. We propose that aldosterone increases the activity of a membrane shuttle system that is regulated by CO2 as found in other H(+)-secreting epithelia. This system may mediate aldosterone-induced changes in colonic H+ transport.


Subject(s)
Aldosterone/pharmacology , Colon/drug effects , Intracellular Membranes/ultrastructure , Animals , Biological Transport , Carbon Dioxide/pharmacology , Carbon Dioxide/physiology , Colon/cytology , Colon/ultrastructure , Cytoplasm/drug effects , Cytoplasm/ultrastructure , Epithelial Cells , Epithelium/drug effects , Epithelium/ultrastructure , Hydrogen/pharmacokinetics , Intracellular Membranes/drug effects , Male , Microscopy, Electron , Rats , Rats, Inbred Strains
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