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S Nielsen

Publications and source records attributed to S Nielsen.

At least 55 records · Page 3Linked to original sources
PubMed2001

Identification of three new splice variants of the SNARE protein SNAP-23.

SNAP-23 has an important role in protein-trafficking processes in mammalian cells and until yet two isoforms of SNAP-23 (SNAP-23a and SNAP-23b) have been described. In the present report, we have identified the existence of three new SNAP-23 isoforms (named SNAP-23c, SNAP-23d, and SNAP-23e), which arise from alternative splicing. By RT-PCR all five splice variants were shown to be expressed in four different human inflammatory cells (eosinophils, basophils, neutrophils, and peripheral blood mononuclear cells). Transfection of the human basophilic KU-812 cell line with plasmid constructs containing the cDNAs of the five splice variants located SNAP-23a and SNAP-23b primarily in the plasma membrane. The other three splice variants were localized both intracellularly and in the plasma membrane.

Alternative Splicing↗
PubMed2001

[Fatal ecstasy intoxication].

A case of full-blown, lethal MDMA intoxication, owing to abuse of ecstasy is described. The increasing popularity of ecstasy among young, otherwise healthy, people prompts health care providers to recognise better the symptoms of systemic intoxication in order to initiate early treatment, such as rehydration, cooling in cases of hyperthermia, seizure treatment, correction of cardiac arrhythmia, and metabolic and electrolyte abnormalities.

Adrenergic Uptake Inhibitors↗
PubMed2001

SNARE proteins are critical for regulated exocytosis of ECP from human eosinophils.

The SNARE hypothesis, describing a protein assembly-disassembly pathway, was recently proposed for the sequential steps of synaptic vesicle docking, activation, and fusion. To determine if SNARE proteins are involved in regulated exocytosis in eosinophils, the presence and functional role of SNAREs was examined in human blood eosinophils. Immunoblotting, subcellular fractionation, and immunocytochemistry documented that vesicle-associated membrane protein-2 (VAMP-2), a vesicle-SNARE, was expressed in human eosinophils. Syntaxin 4 and SNAP-25 were also detected. Sequencing of cloned RT-PCR products amplified from a domain conserved among VAMP isoforms revealed identity only to VAMP-2 but not to VAMP-1 or cellubrevin. Functional experiments revealed that tetanus toxin pretreatment, which cleaved VAMP-2 in eosinophils, significantly inhibited both IgE receptor- and phorbol ester-mediated exocytosis of eosinophil cationic protein (ECP) from streptolysin-O-permeabilized eosinophils. Thus, these results strongly suggest a critical role of SNAREs in regulated exocytosis in eosinophils.

Animals↗
PubMed2001

[Aquaporins in cerebral volume regulation and edema formation].

Regulation of tissue water content and brain volume is of critical importance for the normal functioning of the central nervous system (CNS), which, surrounded by the rigid cranium, is highly sensitive to any increase in the intracranial pressure. Alterations in cerebral water homeostasis and distribution may lead to neuronal and glial swelling known as cytotoxic brain edema, due to accumulation of intracellular water. Although numerous investigations have been performed to elucidate the underlying molecular basis and pathophysiology of brain edema, little is known about the regulation of water transport across the blood-brain barrier and between extra- and intracellular compartments of the brain parenchyma. The discovery and characterization of the aquaporin (AQP) family of membrane water channels provided molecular insight into fundamental processes of water transport across plasma membranes. Two AQPs are expressed abundantly in the mammalian brain: AQP1 in the apical plasma membranes of the cells of choroid plexus in the ventricles, where it has been suggested to participate in the secretion of cerebrospinal fluid and AQP4 in plasma membranes of ependymal cells and astrocytes. The role of AQP4 in the formation of brain oedema was suggested by some recent studies. These findings offer new potentials in brain oedema treatment.

Aquaporins↗
PubMed2001

SNARE proteins are critical for regulated exocytosis of ECP from human eosinophils.

The SNARE hypothesis, describing a protein assembly-disassembly pathway, was recently proposed for the sequential steps of synaptic vesicle docking, activation and fusion. To determine if SNARE proteins are involved in regulated exocytosis in eosinophils, the presence and functional role of SNAREs was examined in human blood eosinophils. Immunoblotting, subcellular fractionation, and immunocytochemistry documented that vesicle-associated membrane protein-2 (VAMP-2), a vesicle-SNARE, was expressed in human eosinophils. Syntaxin 4 and SNAP-25 were also detected. Sequencing of cloned RT-PCR products amplified from a domain conserved among VAMP isoforms revealed identity only to VAMP-2 but not to VAMP-1 or cellubrevin. Functional experiments revealed that tetanus toxin pretreatment, which cleaved VAMP-2 in eosinophils, significantly inhibited both IgE receptor- and phorbol ester-mediated exocytosis of eosinophil cationic protein (ECP) from streptolysin-O-permeabilized eosinophils. Thus, these results strongly suggest a critical role of SNAREs in regulated exocytosis in eosinophils.

Amino Acid Sequence↗
PubMed2001

Detection of monocyte/macrophage cell populations in effusions: a comparative study using flow cytometric immunophenotyping and immunocytochemistry.

The objective of the present study was to compare the efficiency of immunophenotyping using flow cytometry (FCM) and immunocytochemistry (ICC) in the detection of macrophages in serous effusions. Cytoblock sections from 90 effusions were stained for the monocyte/macrophage marker CD14, using ICC. Fresh-frozen samples of all cases were analyzed for CD14 expression, using FCM. Epithelial, lymphoid, and mesothelial cell populations were identified using antibodies against Ber-EP4, CD45, and N-cadherin, respectively. Results were compared with clinical parameters and morphological diagnosis. Thirty-nine specimens were cytologically diagnosed as malignant, containing tumor cells of nonhematologic origin, whereas 46 were interpreted as benign. Two additional specimens were diagnosed as indeterminate or suspicious for malignancy, and 3 specimens contained lymphoma cells. CD14-positive cells were detected in 85/90 (94%) of effusions using FCM, and in all 90 specimens using ICC. The percentage of CD14-positive cells was highly variable, but in some specimens was as high as 76% using FCM and 85% using ICC. A good association was observed between the two methods in the detection of CD14-positive cells (P < 0.001). The presence of macrophages in effusions showed an association with female gender, using both FCM (P = 0.002) and ICC (P = 0.011), but none with effusion site, patient age, clinical and cytological diagnosis, or presence of Ber-EP4-positive cells (P > 0.05). The presence of Ber-EP4-positive cells showed a strong association with the cytological diagnosis of malignancy (P < 0.001). In conclusion, macrophages are a significant cell population in effusions, of both benign and malignant etiology, due to both their size and their possible confusion with cancer cells. Both FCM and ICC aid in the recognition of these cells, and thus provide an effective tool for the identification of different cell populations in effusions.

Adult↗
PubMed2001

Expression of somatostatin receptors on human pituitary adenomas in vivo and ex vivo.

UNLABELLED: The distribution and biologic activity of somatostatin receptor subtypes (SSTR) in pituitary adenomas is not clarified, especially regarding clinically non-functioning adenomas (NFPA). We therefore characterized SSTR in human pituitary adenomas by combining molecular biology and in vivo scintigraphy. Co-expression of gonadotropin-releasing hormone receptor (GnRH-R) mRNA was also assessed to see whether this feature was associated with adenoma subtype and SSTR status. Pituitary tumor biopsies were obtained during transsphenoidal adenomectomy from 21 patients (11 NFPA, 7 acromegalics, 2 prolactinomas, 1 Cushing's disease). Expression of mRNA encoding the 5 known SSTR subtypes and the GnRH-R was determined by RT-PCR. Twelve patients also underwent a pre-operative somatostatin receptor scintigraphy. Most adenomas (no.=18) expressed mRNA for more than one SSTR. SSTR2 mRNA was expressed in 18 cases, whereas SSTR4 was absent in all but one. SSTR3 was frequently expressed in NFPAs. Somatostatin receptor scintigraphy was positive in most cases, and with a significantly higher uptake index in GH-producing adenomas all of which expressed SSTR2 mRNA. The uptake index appeared to be related to receptor density rather than tumor volume. Expression of GnRH-R mRNA was found in both NFPAs and GH-producing adenomas and was not significantly associated with a particular SSTR subtype population. IN CONCLUSION: 1) the distribution of SSTR is not significantly different between NFPA and GH-producing adenomas; and 2) somatostatin receptor scintigraphy reveals a higher uptake in GH-producing adenomas which is not significantly related to either SSTR distribution or tumor volume.

Acromegaly↗
PubMed2001

Epidemiology and mortality of eating disorders.

Although considerable progress has been made over the past 2 decades in the field of eating-disorder epidemiology, there is room for improvement. Eating disorder diagnoses for children, need assessment, prospective longitudinal studies, studies of natural cause, treatment dose-effect studies, and bias are all areas that need careful consideration. Clinicians should consider establishing a Cochrane database for eating disorders. The mortality studies reviewed in this article are dominated by small, sparse, unbalanced data sets, and publication bias and bias caused by loss to follow-up limits the validity of the reported findings. Some methodologic advice is given in the hope that some of the more obvious pitfalls can be avoided in future research.

Adolescent↗
PubMed2001

Randomised phase II trial of pegylated liposomal doxorubicin (DOXIL/CAELYX) versus doxorubicin in the treatment of advanced or metastatic soft tissue sarcoma: a study by the EORTC Soft Tissue and Bone Sarcoma Group.

CAELYX/DOXIL, pegylated liposomal doxorubicin, has shown antitumour activity and reduced toxicity compared with standard doxorubicin in other tumour types. In this prospective randomised trial, 94 eligible patients with advanced soft-tissue sarcoma (STS) were treated, 50 with CAELYX (50 mg/m(2) by a 1 h intravenous (i.v.) infusion every 4 weeks) and 44 with doxorubicin (75 mg/m(2) by an i.v. bolus every 3 weeks). Histological subtypes were evenly matched, 33% were leiomyosarcoma (CAELYX: 18; doxorubicin: 13). Primary disease sites were well matched. CAELYX was significantly less myelosuppressive, only 3 (6%) patients had grade 3 and 4 neutropenia, versus 33 (77%) on doxorubicin; febrile neutropenia occurred in 7 (16%) patients given doxorubicin, but only 1 (2%) given CAELYX. 37 (86%) patients on doxorubicin had grade 2-3 alopecia, but only 3 (6%) on CAELYX, and the major toxicity with CAELYX was to the skin. Palmar-plantar erythrodysesthesia with CAELYX was grade 1: 4 (8%) patients, grade 2: 11 (22%) patients, grade 3: 9 (18%) patients and grade 4: 1 (2%) patient. Other non-haematological grade 3 and 4 toxicities were rare. Confirmed responses were observed with both agents: CAELYX: complete response (CR) 1 (uterine), partial response (PR) 4 (response rate (RR) 10%); and doxorubicin: CR 1, PR 3 (RR of 9%); with the best response being stable disease (NC) in 16 and 18 patients, respectively. The reason for the low response rate is unknown, but it may be due partly to a high proportion of gastrointestinal stromal tumours. In conclusion, CAELYX has equivalent activity to doxorubicin in STS with an improved toxicity profile and should be considered for further investigation in combination with other agents such as ifosfamide.

Adult↗
PubMed2001

Losartan modifies glomerular hyperfiltration and insulin sensitivity in type 1 diabetes.

AIM: The effect of the angiotensin II receptor antagonist losartan on renal haemodynamics and insulin-mediated glucose disposal was examined in normotensive, normoalbuminuric type 1 diabetic patients using a double-blind, placebo-controlled, cross-over design. METHODS: Diurnal blood pressure, glomerular filtration rate (GFR, determined using [125I]-iothalamate), renal plasma flow (RPF, determined using [131I]-hippuran) and urinary albumin excretion rate (UAE) were measured, and a hyperinsulinaemic, euglycaemic clamp with indirect calorimetry was performed in nine patients (age 30 +/- 7 years (mean +/- s.d.), HbA1c 8.1 +/- 1.1%) following 6 weeks' administration of either losartan 50 mg/day or placebo. RESULTS: Diurnal blood pressure was significantly reduced after losartan compared with placebo (122/70 +/- 11/8 vs. 130/76 +/- 12/6 mmHg, p < 0.05). A significant decline in GFR (133 +/- 23 vs. 140 +/- 22 ml/min, p < 0.05) and filtration fraction (FF; GFR/RPF) (24.6 +/- 3.5 vs. 26.2 +/- 3.6%, p < 0.05) was observed in the losartan vs. placebo groups. RPF and UAE did not change. Isotopically determined glucose disposal rates were similar after losartan and placebo in the basal (2.61 +/- 0.53 vs. 2.98 +/- 0.93 mg/kg/min) and insulin-stimulated states (6.84 +/- 2.52 vs. 6.97 +/- 3.11 mg/kg/min). However, the glucose oxidation rate increased significantly after losartan vs. placebo in the basal state (1.72 +/- 0.34 vs. 1.33 +/- 0.18, mg/kg/min, p < 0.01) and during insulin stimulation (2.89 +/- 0.75 vs. 2.40 +/- 0.62 mg/kg/min, p < 0.03). Basal and insulin-stimulated non-oxidative glucose disposal tended to decrease after losartan; however, this was not significant. Endogenous glucose production and lipid oxidation were unchanged after treatment and similarly suppressed during hyperinsulinaemia. Glycaemic control, total cholesterol, high-density lipoprotein (HDL)-cholesterol and triglycerides were stable in both losartan and placebo groups. CONCLUSIONS: Losartan reduces blood pressure, glomerular hyperfiltration and FF, and improves basal and insulin-stimulated glucose oxidation in normotensive, normoalbuminuric type 1 diabetic patients.

Adult↗
PubMed2001

Physiology and pathophysiology of renal aquaporins.

The discovery of aquaporin-1 (AQP1) by Agre and associates answered the longstanding biophysical question of how water specifically crosses biological membranes. In the kidney at least 7 aquaporins are expressed at distinct sites. AQP1 is extremely abundant in the proximal tubule and descending thin limb and is essential for urinary concentration. AQP2 is exclusively expressed in the principal cells of the connecting tubule and collecting duct and is the predominant vasopressin-regulated water channel. AQP3 and AQP4 are both present in the basolateral plasma membrane of collecting duct principal cells and represent exit pathways for water reabsorbed apically via AQP2. Studies in patients and transgenic mice have shown that both AQP2 and AQP3 are essential for urinary concentration. Three additional aquaporins are present in the kidney. AQP6 is present in intracellular vesicles in collecting duct intercalated cells and AQP8 are present intracellularly at low abundance in proximal tubules and collecting duct principal cells but the physiological function of these 2 channels remain undefined. AQP7 is abundant in the brush border of proximal tubule cells and is likely to be involved in proximal tubule water reabsorption. A series of studies have underscored crucial roles of aquaporins for regulation of renal water metabolism and hence body water balance. Moreover it has become clear that dysregulation of aquaporins, and especially AQP2 is critically involved in many water balance disorders. Lack of functional AQP2 is seen in primary forms of diabetes insipidus, and reduced expression and targeting is seen in several diseases associated with urinary concentrating defects such as acquired nephrogenic diabetes insipidus, postobstructive polyuria, as well as acute and chronic renal failure. In contrast, in conditions with water retention such as severe congestive heart failure, pregnancy and SIADH both AQP2 expression levels and apical plasma membrane targetting is increased suggesting a role for AQP2 in the development of water retention. Continued analysis of the aquaporins is providing detailed molecular insight into the fundamental physiology and pathophysiology of water balance and water balance disorders.

Animals↗
PubMed2001

The role of desmin and N-cadherin in effusion cytology: a comparative study using established markers of mesothelial and epithelial cells.

The objective of the present study was to analyze the role of the mesothelial markers desmin and N-cadherin in the diagnostic panel of serous effusions. A total of 181 pleural and peritoneal effusions consisted of 101 cases cytologically diagnosed as malignant (89 carcinomas, 12 mesotheliomas), 78 benign, and 2 inconclusive specimens. All specimens were immunostained using 11 antibodies, against epithelial membrane antigen, Ber-EP4, carcinoembryonic antigen, E-cadherin, CA 125, N-cadherin, desmin, calretinin, p53, vimentin, and CD45. After evaluation of immunocytochemistry results, 110 specimens were diagnosed as malignant (98 carcinomas, 12 mesotheliomas) and 71 as benign (56 cellular, 15 paucicellular). The presence of desmin was detected in benign mesothelial cells in 47 of 56 (84%) reactive cellular specimens compared with 1 of 12 (8%) malignant mesotheliomas and 2 of 98 (2%) carcinomas. N-cadherin was expressed in 48 of 56 (86%) reactive cases, 12 of 12 (100%) mesotheliomas, and 47 of 98 (48%) carcinomas. In carcinomas, N-cadherin expression was most often seen in ovarian carcinoma but was also found in other carcinomas. Calretinin, an established marker of mesothelial cells, was detected in 52 of 56 (93%) reactive specimens, 11 of 12 (93%) mesotheliomas, and 3 of 98 (3%) carcinomas. Evaluation of staining results led to reclassification of six malignant specimens as benign, whereas 17 cases diagnosed as benign and the two diagnosed as inconclusive were classified as malignant. In conclusion, desmin appears to be a promising marker for the distinction between reactive mesothelium and malignant epithelial cells in terms of both specificity and sensitivity, and its complementary use with calretinin is recommended. Unlike calretinin, it may also prove valuable for the distinction between benign and malignant mesothelial cells. N-cadherin does not have a role in the distinction between mesothelial and epithelial cells. However, it may prove useful in the characterization of carcinomas of unknown origin. As has previously been shown, a significant number of diagnoses that are based on morphologic examination alone are modified after the use of a broad antibody panel.

Adolescent↗
PubMed2001

Effects of centrally administered arginine vasopressin and atrial natriuretic peptide on the development of brain edema in hyponatremic rats.

OBJECTIVE: Centrally released arginine vasopressin (AVP) and atrial natriuretic peptide (ANP) have been shown to participate in brain volume regulation. The aim of the present study was to evaluate the effects of centrally administered AVP and ANP on the time course of development of brain edema in vivo in hyponatremic rats, using diffusion-weighted magnetic resonance imaging. METHODS: We performed intracerebroventricular (ICV) administration of 120 microg AVP, 20 microg ANP, or physiological saline into the right lateral ventricle in 18 rats. Twenty-five minutes after the treatment, we induced systemic hyponatremia by the intraperitoneal administration of 140 mmol/L dextrose solution. Serial diffusion-weighted imaging scans were obtained up to 96 minutes after the start of the hyponatremia. Changes in the brain extra-to intracellular volume fraction ratio were estimated as changes in the apparent diffusion coefficient (ADC). RESULTS: No change in the ADC was observed after the ICV injection of saline or AVP. The onset of hyponatremia induced a rapid and marked ADC reduction in both groups, indicating an increased intracellular space. However, the ADC decrease became significantly more pronounced in the ICV AVP group (83.3+/-4.7% of baseline level, mean +/- standard deviation) than in the saline group (93.7+/-3.3% of baseline, P < 0.001) after 78 minutes of hyponatremia. The ICV injection of ANP induced a prompt ADC increase to 111.5+/-10.0% (P < 0.05) of the baseline level, indicating a rapid reduction in the intracellular compartment. In the initial phase of hyponatremia, the ADC values in the ANP group were consistently higher than those in the saline group, decreasing finally to 86.9+/-9.6% after 96 minutes of hyponatremia. CONCLUSION: Our findings demonstrate the opposite effects of AVP and ANP on the intracellular volume fraction of the brain during the development of cellular brain edema, with an immediate effect on ANP and a delayed effect on AVP. The results emphasize the direct effects of these hormones on the cellular volume regulatory mechanisms in the brain during the development of cerebral edema.

Animals↗
PubMed2001

Molecular and functional evidence for electrogenic and electroneutral Na(+)-HCO(3)(-) cotransporters in murine duodenum.

Inward Na(+)-HCO(3)(-) cotransport has previously been demonstrated in acidified duodenal epithelial cells, but the identity and localization of the mRNAs and proteins involved have not been determined. The molecular expression and localization of Na(+)-HCO(3)(-) cotransporters (NBCs) were studied by RT-PCR, sequence analysis, and immunohistochemistry. By fluorescence spectroscopy, the intracellular pH (pH(i)) was recorded in suspensions of isolated murine duodenal epithelial cells loaded with 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein. Proximal duodenal epithelial cells expressed mRNA encoding two electrogenic NBC1 isoforms and the electroneutral NBCn1. Both NBC1 and NBCn1 were localized to the basolateral membrane of proximal duodenal villus cells, whereas the crypt cells did not label with the anti-NBC antibodies. DIDS or removal of extracellular Cl(-) increased pH(i), whereas an acidification was observed on removal of Na(+) or both Na(+) and Cl(-). The effects of inhibitors and ionic dependence of acid/base transporters were consistent with both inward and outward Na(+)-HCO(3)(-) cotransport. Hence, we propose that NBCs are involved in both basolateral electroneutral HCO(3)(-) transport as well as basolateral electrogenic HCO(3)(-) transport in proximal duodenal villus cells.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed2001

Expression and immunolocalization of aquaporin water channels in rat exocrine pancreas.

Both the acinar and ductal cells of the pancreas secrete a near-isotonic fluid and may thus be sites of aquaporin (AQP) water channel expression. Northern blot analysis of mRNA from whole rat pancreas revealed high levels of AQP1 and AQP8 expression, whereas lower levels of AQP4 and AQP5 expression were just detectable by RT-PCR Southern blot analysis. Immunohistochemistry showed that AQP1 is localized in the microvasculature, whereas AQP8 is confined to the apical pole of the acinar cells. No labeling of acinar, ductal, or vascular tissue was detected with antibodies to AQP2-7. With immunoelectron microscopy, AQP8 labeling was observed not only at the apical membrane of the acinar cells but also among small intracellular vesicles in the subapical cytoplasm, suggesting that there may be regulated trafficking of AQP8 to the apical plasma membrane. To evaluate the contribution of AQPs to the membrane water permeability, video microscopy was used to measure the swelling of acinar cells in response to hypotonic stress. Osmotic water permeability was reduced by 90% following exposure to Hg(2+). Since AQP8 is confined to the apical membrane, the marked effect of Hg(2+) suggests that other water channels may be expressed in the basolateral membrane.

Algorithms↗
PubMed2001

Identification and localization of aquaporin water channels in human salivary glands.

Aquaporin (AQP) water channels are expressed in a variety of fluid-transporting epithelia and are likely to play a significant role in salivary secretion. Our aim was to identify and localize the aquaporins expressed in human salivary glands. Total RNA was extracted from human parotid, submandibular, sublingual, and labial glands and from human brain. Expression of aquaporin mRNA was assessed by RT-PCR using specific primers for human AQP1, AQP3, AQP4, and AQP5. All four aquaporins were detected by RT-PCR in all of the glands, and the sequences were confirmed after further amplification with nested primers. Cleaned PCR products were then used as (32)P-labeled cDNA probes in a semiquantitative Northern blot analysis using glyceraldehyde-3-phosphate dehydrogenase as reference. Only AQP1, AQP3, and AQP5 mRNAs were present at significant levels. AQP localization was determined by immunohistochemistry on paraffin sections using affinity-purified primary antibodies and peroxidase-linked secondary antibodies. Each salivary gland type showed a broadly similar staining pattern: AQP1 was localized to the capillary endothelium and myoepithelial cells; AQP3 was present in the basolateral membranes of both mucous and serous acinar cells; AQP4 was not detected; and AQP5 was expressed in the luminal and canalicular membranes of both types of acinar cell. We conclude that AQP3 and AQP5 together may provide a pathway for transcellular osmotic water flow in the formation of the primary saliva.

Antibodies↗
PubMed2001

Altered expression of renal aquaporins and Na(+) transporters in rats treated with L-type calcium blocker.

Nifedipine, a calcium antagonist, has diuretic and natriuretic properties. However, the molecular mechanisms by which these effects are produced are poorly understood. We examined kidney abundance of aquaporins (AQP1, AQP2, and AQP3) and major sodium transporters [type 3 Na/H exchanger (NHE-3); type 2 Na-Pi cotransporter (NaPi-2); Na-K-ATPase; type 1 bumetanide-sensitive cotransporter (BSC-1); and thiazide-sensitive Na-Cl cotransporter (TSC)] as well as inner medullary abundance of AQP2, phosphorylated-AQP2 (p-AQP2), AQP3, and calcium-sensing receptor (CaR). Rats treated with nifedipine orally (700 mg/kg) for 19 days had a significant increase in urine output, whereas urinary osmolality and solute-free water reabsorption were markedly reduced. Consistent with this, immunoblotting revealed a significant decrease in the abundance of whole kidney AQP2 (47 +/- 7% of control rats, P < 0.05) and in inner medullary AQP2 (60 +/- 7%) as well as in p-AQP2 abundance (17 +/- 6%) in nifedipine-treated rats. In contrast, whole kidney AQP3 abundance was significantly increased (219 +/- 28%). Of potential importance in modulating AQP2 levels, the abundance of CaR in the inner medulla was significantly increased (295 +/- 25%) in nifedipine-treated rats. Nifedipine treatment was also associated with increased urinary sodium excretion. Consistent with this, semiquantitative immunoblotting revealed significant reductions in the abundance of proximal tubule Na(+) transporters: NHE-3 (3 +/- 1%), NaPi-2 (53 +/- 12%), and Na-K-ATPase (74 +/- 5%). In contrast, the abundance of the distal tubule Na-Cl cotransporter (TSC) was markedly increased (240 +/- 29%), whereas BSC-1 in the thick ascending limb was not altered. In conclusion, 1) increased urine output and reduced urinary concentration in nifedipine-treated-rats may, in part, be due to downregulation of AQP2 and p-AQP2 levels; 2) CaR might be involved in the regulation of water reabsorption in the inner medulla collecting duct; 3) reduced expression of proximal tubule Na(+) transporters (NHE-3, NaPi-2, and Na, K-ATPase) may be involved in the increased urinary sodium excretion; and 4) increase in TSC expression may occur as a compensatory mechanism.

Animals↗