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C Westenfelder

Publications and source records attributed to C Westenfelder.

At least 19 recordsLinked to original sources
PubMed2000

Erythropoietin stimulates proliferation of human renal carcinoma cells.

BACKGROUND: We reported recently that normal human, rat, and mouse tubular cells express authentic erythropoietin-receptors (EPO-R) through which EPO stimulates mitogenesis. The present study examines whether EPO could elicit such a proliferative and thereby potentially detrimental response in cells of human renal-cell carcinoma (RCC). METHODS: Nephrectomy samples were screened from patients with RCC (one chromophilic, two clear cell) as well as cell lines of human (Caki-2, 786-0) and mouse (RAG) renal adenocarcinomas for expression of EPO-R transcripts and protein. Cells were further tested for specific 125I-EPO binding and mitogenic response to EPO. RESULTS: Authentic EPO-R transcripts and protein (approximately 72 kD) were detected in renal tumors and cell lines. Tumors showed low-level EPO expression, while cell lines did not. In cells, specific 125I-EPO binding to a single class of EPO-R (apparent Kd 1. 3 to 1.4 nmol/L, Bmax 2.2 to 2.6 fmol/mg protein) was observed. EPO stimulated cell proliferation dose dependently, and the individual mitogenic effects of either EPO or 10% newborn calf serum were markedly amplified when both were coadministered. CONCLUSION: These data are the first to demonstrate, to our knowledge, that human RCCs express EPO-R message and protein and that receptor activation stimulates their proliferation in vitro. If these mitogenic effects of EPO are also operative in patients with RCC, endogenous EPO or its administration for the treatment of anemia could potentially hasten proliferation of renocellular malignancies.

Adenocarcinoma, Clear Cell↗
PubMed1999

Human, rat, and mouse kidney cells express functional erythropoietin receptors.

BACKGROUND: Erythropoietin (EPO), secreted by fibroblast-like cells in the renal interstitium, controls erythropoiesis by regulating the survival, proliferation, and differentiation of erythroid progenitor cells. We examined whether renal cells that are exposed to EPO express EPO receptors (EPO-R) through which analogous cytokine responses might be elicited. METHODS: Normal human and rat kidney tissue and defined cell lines of human, rat, and mouse kidney were screened, using reverse transcription-polymerase chain reaction, nucleotide sequencing, ligand binding, and Western blotting, for the expression of EPO-R. EPO's effects on DNA synthesis and cell proliferation were also examined. RESULTS: EPO-R transcripts were readily detected in cortex, medulla, and papilla of human and rat kidney, in mesangial (human, rat), proximal tubular (human, mouse), and medullary collecting duct cells (human). Nucleotide sequences of EPO-R cDNAs from renal cells were identical to those of erythroid precursor cells. Specific 125I-EPO binding revealed a single class of high- to intermediate-affinity EPO-Rs in each tested cell line (kD 96 pm to 1. 4 nm; Bmax 0.3 to 7.0 fmol/mg protein). Western blots of murine proximal tubular cell membranes revealed an EPO-R protein of approximately 68 kDa. EPO stimulated DNA synthesis and cell proliferation dose dependently. CONCLUSION: This is the first direct demonstration, to our knowledge, that renal cells possess EPO-Rs through which EPO stimulates mitogenesis. This suggests currently unrecognized cytokine functions for EPO in the kidney, which may prove beneficial in the repair of an injured kidney while being potentially detrimental in renal malignancies.

Animals↗
PubMed1998

Increased reabsorptive capacity after ureteral obstruction reduces the ability of glucose to inhibit phosphate reabsorption in rat kidney.

BACKGROUND: Proximal tubular reabsorption of glucose (G), phosphate (Pi) and amino acids is energized by the transmembrane Na+ gradient, which explains why decreased concentration of one solute can enhance the transport of another. Accordingly, we postulated that the consistent increase in Pi reabsorption seen in the post-obstructed kidney (POK) could be caused, in part, by the low filtered load of glucose and reversed by glucose loading. METHODS: Renal function was examined before and after i.v. glucose loading in POKs (after release of 24 h of unilateral ureteral obstruction) and control kidneys (CK) of 10 adult rats. Brush-border membrane vesicle (BBMV) transports of Pi and glucose were assessed in POKs and CKs. RESULTS: In POKs GFR, urine flow and Na+ excretion were significantly reduced and tubular reabsorption of both Pi (T(P)/GFR) and glucose (TG/GFR) were significantly increased: T(P)/GFR, 2.0 +/- 0.2 vs 1.36 +/- 0.1; TmG/GFR, 23.4 +/- 1.7 vs 18.9 +/- 1.1 mmol/l. Glucose loading inhibited T(P)/GFR only in the CK. Initial Na+ gradient-dependent uptakes of D-glucose and Pi were similar in BBMVs from POK and CK. CONCLUSIONS: The increases in T(P)/GFR and TG/GFR seen in the POK do not result from decreased glucose delivery or from alterations in BBM Pi and glucose transporters. The reduced ability of glucose to inhibit Pi reabsorption in the POK results primarily from a generalized increase in proximal tubular reabsorption of Na+ and cotransported Pi and glucose. A specific rise in distal Pi transport capacity may be an additional adaptive response to the low filtered load of Pi in the POK. In addition, absent distal glucose reabsorption may further facilitate Pi reclamation at these sites.

Animals↗
PubMed1996

Urea induces the heat shock response in human neuroblastoma cells.

Uremic encephalopathy is a complication of renal failure that reflects stresses exerted by as yet poorly defined uremic toxins. All cells respond to stresses by undergoing the "heat shock" response. Although urea kinetics and creatinine concentration are routinely used to assess dialysis adequacy, the roles of urea and creatinine as uremic toxins remain controversial. To investigate their potential roles in uremic encephalopathy, cultured human neuroblastoma cells (SK-N-SH) were exposed to 0.5 to 14 mg/dL creatinine, or to 20 to 200 mg/dL urea, or to mannitol, NaCl, or glycerol at equivalent osmolalities for 30 min to 48 h, and the induction of Hsp72 (heat shock) protein was used as a marker of cell stress. Although creatinine failed to elicit a heat shock response, urea in clinically relevant concentrations (40 to 200 mg/dL) induced it at 30 min. The response peaked at 10 h and returned to zero by 48 h. Cells exposed to equivalent osmolalities of mannitol, NaCl, or glycerol failed to exhibit this response. Protein extracts from cells exposed to urea showed significant carbamylation that increased as a function of time. These results demonstrate: (1) that urea is neurotoxic in vitro and that creatinine is not: (2) that the insult urea causes is not simply the result of hypertonicity; but rather (3) that urea, via breakdown to cyanate and ammonium ions, may cause cell stress because of its ability to cause carbamylation of cellular proteins. The cells attenuation of the heat shock response after 10 h of exposure to urea suggests that they can adapt to the presence of urea or carbamylation. This may explain, in part, why the same degree of azotemia causes fewer neurological symptoms in patients with chronic as opposed to acute renal failure.

Blotting, Western↗
PubMed1994

Estimation of renal interstitial adenosine and purine metabolites by microdialysis.

It has been proposed that adenosine, derived from ATP and released into the renal interstitium, mediates a reduction in renal function in ischemic acute renal failure. Because no direct measurements of interstitial adenosine are available, we evaluated an in vivo microdialysis technique to assess the levels of adenosine and its metabolites in the cortex of the normal rat kidney (n = 6). Microdialysis probe implantation did not alter cortical renal blood flow, glomerular filtration rate, or fractional sodium excretion. The interstitial concentration of adenosine was 199 +/- 53 nM, and relative concentrations of inosine, hypoxanthine, xanthine, and uric acid were 99 +/- 47, 182 +/- 29, and 183 +/- 70 nM and 1.8 +/- 0.4 microM, respectively. Infusion of ATP-MgCl2 (n = 5) resulted in a significant increase in the dialysate levels of adenosine (67 +/- 11 to 378 +/- 97 nM), inosine (230 +/- 102 to 803 +/- 219 nM), and uric acid (3.5 +/- 1.3 to 6.9 +/- 1.7 microM). In conclusion, this study demonstrates that the microdialysis technique is suited to monitor metabolically important substances in the renal interstitium.

Adenosine↗
PubMed1992

Evidence for cytokine-inducible nitric oxide synthesis from L-arginine in patients receiving interleukin-2 therapy.

An interferon-gamma, tumor necrosis factor, and interleukin-1-inducible, high-output pathway synthesizing nitric oxide (NO) from L-arginine was recently identified in rodents. High-dose interleukin-2 (IL-2) therapy is known to induce the same cytokines in patients with advanced cancer. Therefore, we examined renal cell carcinoma (RCC; n = 5) and malignant melanoma (MM; n = 7) patients for evidence of cytokine-inducible NO synthesis. Activity of this pathway was evaluated by measuring serum and urine nitrate (the stable degradation product of NO) during IL-2 therapy. IL-2 administration caused a striking increase in NO generation as reflected by serum nitrate levels (10- and 8-fold increase [P less than 0.001, P less than 0.003] for RCC and MM patients, respectively) and 24-h urinary nitrate excretion (6.5- and 9-fold increase [both P less than 0.001] for RCC and MM patients, respectively). IL-2-induced renal dysfunction made only a minor contribution to increased serum nitrate levels. Metabolic tracer studies using L-[guanidino-15N2]arginine demonstrated that the increased nitrate production was derived from a terminal guanidino nitrogen atom of L-arginine. Our results showing increased endogenous nitrate synthesis in patients receiving IL-2 demonstrate for the first time that a cytokine-inducible, high-output L-arginine/NO pathway exists in humans.

Adult↗
PubMed1990

Volume homeostasis in calves with artificial atria and ventricles.

We examined whether replacement of cardiac atria and ventricles with total artificial hearts (TAH), a procedure that removes cardiac nerves and all sources of atrial natriuretic factor (ANF), would cause alterations in volume homeostasis in awake calves. Preoperatively, extracted plasma immunoreactive (ir)ANF levels were 13.3 +/- 0.6 and remained postoperatively at 10.5 +/- 0.4 pg/ml (P less than 0.01). TAH implantation caused systemic and pulmonary hypertension (P less than 0.01), salt retention, edema, and significant elevations of plasma renin, aldosterone, and arginine vasopressin. In intact calves rapid infusion of 6 liters of normal saline raised irANF levels to 73.7 +/- 6.5 pg/ml (P less than 0.01) and elicited a large natriuresis and diuresis. No such response to 6 liters of normal saline was obtained after calves had recovered from TAH implantation. Reduction of cardiac output (CO) by 50% caused further salt retention and no change in irANF levels. Elevation of CO back to and 33% above base line produced only a diuresis, whereas salt retention persisted and irANF levels remained unchanged. The same maneuvers elicited in surgical control calves (artificial ventricles only, largely intact atria) a significant increase in irANF levels and a diuresis and natriuresis. In conclusion, alterations in volume homeostasis observed after TAH implantation seem to be the consequence of at least two pathophysiological mechanisms: 1) functional ANF "deficiency," characterized by apparently unregulated ANF secretion from noncardiac sites, and 2) cardiac denervation.

Animals↗
PubMed1989

Secretion of atrial natriuretic peptide (ANP) from fish atrial and ventricular myocytes in tissue culture.

Primary cultures of atrial and ventricular myocytes (approx. 1 x 10(5) cells/culture) were prepared from adult teleost fish Gila atraria and maintained for 10 days. Immunoreactive atrial natriuretic peptide (ir-ANP) from fish atrial and ventricular cells was 3.9 and 2.8 ng/culture respectively, values not significantly different. Atriocytes from rat and mouse secreted comparable amounts of ANP which were not significantly different from atrial fish cultures (5.2 and 4.3 ng/culture). In contrast, their ventricular myocytes secreted only small quantities of ANP (0.8 and 0.3 ng/culture). When analyzed by reversed-phase HPLC, the media of both fish atrial and ventricular myocytes contained a peptide which exhibited properties similar to authentic human ANP (Ser 99-Tyr 126), suggesting a significant degree of sequence homology between fish and mammalian ANP. Fish ventricular cells, unlike normal mammalian ventricular cells, secrete substantial quantities of immunoreactive-ANP.

Animals↗
PubMed1988

In vivo renal angiotensin converting enzyme activity decreases in glycerol-induced acute renal failure.

We previously demonstrated that intrarenal angiotensin II generation during glycerol-induced acute renal failure was attenuated, which may have resulted from the inability of intrarenal converting enzyme to convert renal angiotensin I to angiotensin II. In order to test this hypothesis in vivo, we determined the ability of the kidney to convert angiotensin I to angiotensin II by measuring the decrease in renal cortical blood flow (RCBF) in response to exogenous angiotensin I administration. Changes in RCBF were monitored by laser-Doppler velocimetry. Three groups of rats were studied: Group I, controls (N = 7); 24 hours prior to study Group II animals were injected with 50% glycerol, 8 ml/kg i.m. (N = 4); and Group III rats were injected with mercuric chloride, 3 mg/kg s.c. (N = 5). All experimental animals had a three- to sixfold rise in serum creatinine. Mean glomerular filtration rate (GFR) of the left and right kidney in control rats was 0.7 and 0.7 ml/min, respectively. Twenty-four hours after glycerol, GFR was 0.2 ml/min in the left kidney and 0.2 ml/min in the right kidney. In HgCl2 treated rats GFR was 0.1 ml/min in the left kidney and 0.1 ml/min in the right kidney. Each of the following maneuvers elicited a similar rise in blood pressure in Groups I through III. Specifically, when first angiotensin I (4 micrograms/kg/min) was infused for three minutes; second, when 10 minutes later angiotensin I (5 micrograms) was directly applied on the left kidney; and third, when angiotensin II (5 micrograms) was topically administered.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Kidney Injury↗
PubMed1988

Atrial natriuretic factor and salt adaptation in the teleost fish Gila atraria.

It is unknown whether atrial natriuretic factor (ANF) is a mediator of environmental salt tolerance in euryhaline teleost fish. This was investigated in anesthetized Gila atraria, a euryhaline teleost native to springs of pleistocene Lake Bonneville. Plasma levels of immunoreactive (ir) ANF [using anti-human ANF-(99-126) antibodies] in fish obtained from a "fresh water" spring were significantly lower (146 +/- 27) than those in fish obtained from a "1% NaCl" spring (347 +/- 21 pg/ml, P less than 0.01). Electron micrographs of fish atrial and ventricular cardiocytes demonstrated many perinuclear granules, which closely resembled ANF-containing secretory granules seen in mammalian atriocytes. Fish heart extract contained ANF-like material of 3 kDa, which caused a marked diuresis and natriuresis in rats. In a second study, fish from a 1% NaCl spring were kept in tanks. One-third of the fish were maintained in 1% NaCl and one-third each were either adapted to fresh- or high-salt water. After 12 days, plasma irANF levels in 1% NaCl fish were 343 +/- 55, in fresh water fish 213 +/- 20 and in high-NaCl fish 691 +/- 79 pg/ml. These values differed significantly from each other (P less than 0.01). There was a close correlation between plasma irANF levels and both environmental and internal salt concentration. These data suggest that piscine ANF is an as yet unrecognized mediator of salt tolerance in this teleost and that ANF in these animals closely resembles mammalian ANF.

Acclimatization↗
PubMed1988

Effects of triiodothyronine replacement on the anemia of chronic renal failure.

Patients and/or experimental animals with chronic renal failure have decreased serum levels of triiodothyronine (T3), a hormone well known for its erythropoietic activity. The following studies were designed in order to determine whether this observed abnormality in T3 metabolism is an important contributory factor to the etiology of the anemia of uremia. Groups of rats were made chronically uremic by a standard 5/6 nephrectomy technique and received slightly above physiological doses of T3 either by intermittent S.C. injections (twice daily) or by continuous infusion from intraperitoneally implanted osmotic minipumps. After 2 weeks of such treatment, and despite a normalization of serum T3 levels, there were no significant changes in the hematocrit, individual red cell mass, or serum erythropoietin levels of the uremic animals given T3 compared to control rats. We conclude that (1) the decreased serum T3 levels observed in uremia are not an important contributory factor to the pathogenesis of the anemia, and (2) treatment with replacement doses of T3 does not result in significant improvement of erythropoiesis.

Anemia↗
PubMed1987

The kidney in hypergammaglobulinemic purpura.

A 25-year-old woman with long-standing hypergammaglobulinemic purpura developed distal renal tubular acidosis and a urine-concentrating defect. The acidification defect was characterized as suggestive of impaired distal proton secretion by infusion of neutral phosphate. The concentrating defect was a form of acquired nephrogenic diabetes insipidus. On renal biopsy, IgM mesangial nephropathy was found along with multiple large hyaline tubular casts. The renal findings in hypergammaglobulinemic purpura are reviewed.

Adult↗
PubMed1987

Failure of angiotensin converting enzyme inhibition to affect the course of chronic puromycin aminonucleoside nephropathy.

The effects of the angiotensin converting enzyme (ACE) inhibitor enalapril on the proteinuria and degree of focal glomerular sclerosis hyalinosis (FSH) in chronic puromycin aminonucleoside nephropathy (PAN) were examined. Chronic PAN was induced in male Sprague-Dawley rats by seven subcutaneous injections of puromycin aminonucleoside (20 mg/kg) over 10 weeks (Groups I and II). Group II rats also received enalapril 10 mg/kg/day in the drinking water throughout the study (12 weeks). Group III rats served as age-matched controls. Proteinuria was similar in Groups I and II (35.5 +/- 9.7 versus 29.1 +/- 4.1 mg protein/mg creatinine, mean +/- SEM, P greater than 0.05). Serum creatinine remained unchanged in Group I, but rose from 0.7 +/- 0.04 to 1.2 +/- 0.1 mg/dl (mean +/- SEM, P less than 0.05) in Group II. FSH was 13.8% in Group I, 12.9% in Group II (P greater than 0.05), and 0.6% in Group III. There was no significant difference in glomerular lipid content and in immunofluorescence for rat albumin, fibrinogen, IgM, IgG, and C3 between Groups I and II. ACE activity was inhibited by 94% in serum, 83% in lungs, and 92% in kidneys; and blood pressure response to. Angiotensin I challenge was decreased by 50% in rats similarly treated with enalapril versus controls. In summary, proteinuria and glomerular sclerosis in this model are not affected by ACE inhibition.

Angiotensin I↗
PubMed1983

Effect of vanadate on water transport by the toad bladder.

Vanadate increases renal Na and water excretion. The mechanism whereby vanadate impairs water transport was examined in the toad bladder. Vanadate did not alter baseline water transport but caused a significant inhibition of water transport elicited by high doses of AVP. The inhibition of AVP stimulated water flow by vanadate was dose dependent with inhibition present with concentration as low as 10(-7) and maximal inhibition occurring at 10(-5) M. Vanadate also inhibited water transport stimulated by cyclic AMP or by phosphodiesterase inhibition indicating that vanadate has an effect beyond cyclic AMP step, in addition to whatever effect it might have on adenylate cyclase. The inhibitory effect of vanadate on AVP stimulated water flow was not altered by prior Na-K-ATPase or prostaglandin inhibition. Since vanadate has been shown to stimulate adenylate cyclase in other tissues we examined whether addition of vanadate 10 minutes after addition of AVP would enhance water transport. Vanadate caused a transient enhancement of AVP stimulated water flow. These data demonstrate that vanadate can inhibit or stimulate water flow in the toad bladder.

1-Methyl-3-isobutylxanthine↗