Prostaglandin E(2) interaction with AVP: effects on AQP2 phosphorylation and distribution

Prostaglandin E(2) (PGE(2)) antagonizes the action of arginine vasopressin (AVP) on collecting duct water permeability. To investigate the mechanism of this antagonism, rat renal inner medulla (IM) was incubated with the two hormones, and the phosphorylation and subcellular distribution of the water channel, aquaporin-2 (AQP2) were studied. Using a phosphorylation state-specific AQP2 antibody, we demonstrated that AVP stimulates AQP2 phosphorylation at the Ser(256) protein kinase A consensus site in a time- and dose-dependent manner. In parallel studies using a differential centrifugation technique, we demonstrated that AVP induced translocation of AQP2 from an intracellular vesicle-enriched fraction to a plasma membrane-enriched fraction. PGE(2) (10(-7) M) added after AVP (10(-8) M) did not decrease AQP2 phosphorylation but reversed AVP-induced translocation of AQP2 to the plasma membrane. Preincubation of IM with PGE(2) did not prevent the effects of AVP on AQP2 phosphorylation and trafficking. PGE(2) alone did not influence AQP2 phosphorylation and subcellular distribution. Our data indicate that 1) recruitment of AQP2 to the plasma membrane and its retrieval to a pool of intracellular vesicles may be regulated independently, 2) PGE(2) may counteract AVP action by activation of AQP2 retrieval, 3) dephosphorylation of AQP2 is not a prerequisite for its internalization.

Decreased vasopressin-mediated renal water reabsorption in rats with chronic aldosterone-receptor blockade

Previous studies have suggested that mineralocorticoids are needed for a normal action of vasopressin on collecting duct osmotic water permeability. However, the mechanisms behind this are unknown. To investigate if aldosterone-receptor blockade influences vasopressin type 2 receptor (V(2))-mediated renal water reabsorption and the renal expression of the vasopressin-regulated water channel aquaporin-2 (AQP2), rats were treated with the aldosterone-receptor antagonist canrenoate (20 mg/day iv) for 4 wk. Daily urine flow was increased significantly by 44%, and urine osmolality was decreased by 27% in canrenoate-treated rats. Acute V(2)-receptor blockade (OPC-31260, 800 microgram. kg(-1). h(-1)) was performed under conditions in which volume depletion was prevented. In control rats, OPC-31260 induced a significant increase in urine flow rate (V, +25%) and free water clearance (C(H(2)O), -29%). In canrenoate-treated rats, the effect of OPC-31260 was significantly reduced, and semiquantiative immunoblotting demonstrated a significant reduction (45%) in AQP2 expression. Because rats with common bile duct ligation (CBL) have a reduced vasopressin-mediated water reabsorption compared with normal rats (V: -24%; C(H(2)O): -28%, and 86% downregulation of AQP2), the effect of canrenoate combined with OPC-31260 was tested. Canrenoate treatment of CBL rats significantly increased daily urine flow, decreased urine osmolality, and impaired the aquaretic response to OPC-31260 (V: -23%; C(H(2)O): -31%) with maintained suppression of the renal AQP2 expression. Thus canrenoate treatment of normal and CBL rats showed 1) increased urine production, 2) reduced aquaretic effect of acute V(2)-receptor blockade, and 3) a marked reduction in AQP2 expression. This strongly supports the view that aldosterone plays a significant role for vasopressin-mediated water reabsorption.

Immunoelectron microscopic localization of NBC3 sodium-bicarbonate cotransporter in rat kidney

In the present study, we produced a rabbit peptide-derived polyclonal COOH-terminal antibody that selectively recognizes NBC3, to determine the cellular and subcellular localization of NBC3 in rat kidney, using immunocytochemistry and immunoelectron microscopy. Immunocytochemistry with cryostat sections and semithin cryosections revealed specific staining of intercalated cells (ICs) in the connecting tubule and in cortical, outer medullary, and initial inner medullary collecting ducts. In the connecting tubule and in the cortical and medullary collecting duct, the labeling was associated with both type A and type B ICs. In type A ICs, labeling was confined to the apical and subapical domains, whereas in type B ICs, basal domains were exclusively labeled. In contrast, collecting duct principal cells were consistently unlabeled, and this was confirmed using anti-aquaporin-2 antibodies, which labeled principal cells in parallel semithin cryosections. Glomeruli, proximal tubules, descending thin limbs, ascending thin limbs, thick ascending limbs, distal convoluted tubules, and vascular structures were unlabeled. For immunoelectron microscopy, tissue samples were freeze-substituted, and immunolabeling was performed on ultrathin Lowicryl HM20 sections. Immunoelectron microscopy demonstrated that NBC3 labeling was very abundant in the apical plasma membrane, in intracellular vesicles, and in tubulocisternal profiles in the subapical domains of type A ICs. In type B ICs, NBC3 was mainly present in the basolateral plasma membrane. Immunolabeling controls using peptide-absorbed antibody were consistently negative. In conclusion, NBC3 is highly abundant in the apical plasma membrane of type A ICs and in the basolateral plasma membrane of type B ICs. This suggests that NBC3 plays an important role in modulating bicarbonate transport in the connecting tubule and collecting duct.

Cellular localization of P2Y(2) purinoceptor in rat renal inner medulla and lung

Physiological and pharmacological studies have demonstrated that extracellular ATP, acting through P2Y(2) purinoceptor, modulates water permeability of renal medullary collecting duct cells and the secretion of ions, mucin, and surfactant phospholipids by respiratory epithelia. Here we provide direct molecular evidence for the expression of P2Y(2) purinoceptor in these cells. RT-PCR confirmed P2Y(2) purinoceptor mRNA expression in rat lung and kidney and demonstrated expression in renal collecting ducts. Northern analysis showed that both lung and kidney express one 3.6-kb P2Y(2) purinoceptor mRNA transcript. Immunoblots using peptide-derived polyclonal antibody to P2Y(2) purinoceptor showed that inner medullary collecting ducts (IMCD) express two distinct and specific products (47 and 105 kDa) and account for the majority of the receptor expression in inner medulla, whereas the 105-kDa form is predominant in lung. Immunoperoxidase labeling on cryosections showed localization of receptor protein in the apical and basolateral domains of IMCD principal cells and in the secretory cells (Clara cells and goblet cells) of the terminal respiratory bronchioles.

Localization and regulation of PKA-phosphorylated AQP2 in response to V(2)-receptor agonist/antagonist treatment

Phosphorylation of Ser(256), in a PKA consensus site, in AQP2 (p-AQP2) appears to be critically involved in the vasopressin-induced trafficking of AQP2. In the present study, affinity-purified antibodies that selectively recognize AQP2 phosphorylated at Ser(256) were developed. These antibodies were used to determine 1) the subcellular localization of p-AQP2 in rat kidney and 2) changes in distribution and/or levels of p-AQP2 in response to [desamino-Cys(1),D-Arg(8)]vasopressin (DDAVP) treatment or V(2)-receptor blockade. Immunoelectron microscopy revealed that p-AQP2 was localized in both the apical plasma membrane and in intracellular vesicles of collecting duct principal cells. Treatment of rats with V(2)-receptor antagonist for 30 min resulted in almost complete disappearance of p-AQP2 labeling of the apical plasma membrane with only marginal labeling of intracellular vesicles remaining. Immunoblotting confirmed a marked decrease in p-AQP2 levels. In control Brattleboro rats (BB), lacking vasopressin secretion, p-AQP2 labeling was almost exclusively present in intracellular vesicles. Treatment of BB rats with DDAVP for 2 h induced a 10-fold increase in p-AQP2 labeling of the apical plasma membrane. The overall abundance of p-AQP2, however, was not increased, as determined both by immunoelectron microscopy and immunoblotting. Consistent with this, 2 h of DDAVP treatment of normal rats also resulted in unchanged p-AQP2 levels. Thus the results demonstrate that AQP2 phosphorylated in Ser(256) is present in the apical plasma membrane and in intracellular vesicles and that both the intracellular distribution/trafficking, as well as the abundance of p-AQP2, are regulated via V(2) receptors by altering phosphorylation and/or dephosphorylation of Ser(256) in AQP2.

Regulated exocytosis in immune function: are SNARE-proteins involved?

Inflammation is an important feature in the pathogenesis of most chronic lung diseases. It is characterized by tissue infiltration with various inflammatory cells, including eosinophils, mast cells, basophils, macrophages, neutrophils, T- and B-lymphocytes and dendritic cells (1). In the tissue granulocytes release their toxic granule proteins after being stimulated by soluble mediators released by other inflammatory cells (2). Therefore, it is important to characterize the intracellular mechanisms regulating the transport of the granule contents in inflammatory cells. Intracellular vesicle-traffic in mammalian cells is mediated by transport vesicles that emerge from donor compartments and are specifically targeted to acceptor compartments where they deliver their contents after membrane fusion (3). This traffic leads to three types of fusion: vesicle-intracellular membranes, vesicle-vesicle or vesicle-plasma membrane. The process leading to fusion of vesicle-plasma membrane is called exocytosis, and it delivers proteins to the cell surface (receptors e.g. CD11b, CD18) and exports soluble molecules (mediators e.g. ECP) from the cell. A number of key proteins involved in regulated exocytosis have been identified from inflammatory cells. This review is a brief summary of these proteins and it includes recent results from studies on regulated exocytosis in inflammatory cells.

NBC3 expression in rabbit collecting duct: colocalization with vacuolar H+-ATPase

We have recently cloned and characterized a unique sodium bicarbonate cotransporter, NBC3, which unlike other members of the NBC family, is ethylisopropylamiloride (EIPA) inhibitable, DIDS insensitive, and electroneutral (A. Pushkin, N. Abuladze, I. Lee, D. Newman, J. Hwang, and I. Kurtz. J. Biol. Chem. 274: 16569-16575, 1999). In the present study, a specific polyclonal antipeptide COOH-terminal antibody, NBC3-C1, was generated and used to determine the pattern of NBC3 protein expression in rabbit kidney. A major band of approximately 200 kDa was detected on immunoblots of rabbit kidney. Immunocytochemistry of rabbit kidney frozen sections revealed specific staining of the apical membrane of intercalated cells in both the cortical and outer medullary collecting ducts. The pattern of NBC3 protein expression in the collecting duct was nearly identical to the same sections stained with an antibody against the vacuolar H+-ATPase 31-kDa subunit. In addition, the NBC3-C1 antibody coimmunoprecipitated the vacuolar H+-ATPase 31-kDa subunit. Functional studies in outer medullary collecting ducts (inner stripe) showed that type A intercalated cells have an apical Na+-dependent base transporter that is EIPA inhibitable and DIDS insensitive. The data suggest that NBC3 participates in H+/base transport in the collecting duct. The close association of NBC3 and the vacuolar H+-ATPase in type A intercalated cells suggests a potential structural/functional interaction between the two transporters.

Muscle mass and function in thyrotoxic patients before and during medical treatment

OBJECTIVE

Development of muscle weakness and atrophy are well known complications of thyrotoxicosis, although little is known about its clinical course. The present longitudinal study was therefore undertaken to monitor muscle mass and strength before and during treatment of hyperthyroidism.

DESIGN AND PATIENTS

Five patients (2 male, 3 female; Age 41 +/- 6 years; BMI 22.2 +/- 1.1 kg/m2) with newly diagnosed hyperthyroidism were studied with respect to muscle area, muscle strength, body composition and substrate metabolism at baseline and after 1, 3, 6, 9 and 12 months of treatment.

MEASUREMENTS

Midthigh muscle areas were assessed by computed tomography (CT), while bioelectrical impedance analysis (BIA) was used for assessment of body composition. The isometric strength of the biceps brachialis and quadriceps muscles was assessed by means of a dynamometer and the maximal static ins- and ex-piratory mouth pressures were measured with a respiratory pressure module.

RESULTS

Prior to treatment thyrotoxic patients all displayed elevated levels of total and free T3 and T4 together with suppressed TSH. BMI, fat mass and lean body mass increased significantly during the treatment period, while energy expenditure (EE) decreased. Thigh muscle areas increased by 24% (101.5 +/- 11.5 vs. 125.3 +/- 13.1 cm2, P < 0.05) from entry to peak. Peak time was 9 +/- 0.9 months. During treatment a significant (P < 0.01) increase in muscle strength was observed; arm capacity increased by 48%, while leg capacity increased by 51%. Peak time (months) was: Right arm: 8 +/- 3, left arm: 7 +/- 2, right leg: 5 +/- 3, left leg: 9 +/- 2. Respiratory muscle strength, expressed as maximal ins- or ex-piratory mouth pressure, was significantly impaired among patients at entry. A significant increase in inspiratory and expiratory strength was found from entry to peak (P < 0.05), as inspiratory strength increased by 35% and expiratory by 19%. Inspiratory strength peaked after 7 +/- 1 months, expiratory muscle strength after 6 +/- 1 months.

CONCLUSIONS

In conclusion we find that in patients with thyrotoxicosis muscle mass is reduced by approximately 20% and muscle strength by approximately 40% and that between 5 and 9 months elapse before normal muscle mass and function are reestablished.

Cellular and subcellular immunolocalization of ClC-5 channel in mouse kidney: colocalization with H+-ATPase

To determine the immunolocalization of ClC-5 in the mouse kidney, we developed a ClC-5-specific rat monoclonal antibody. Immunoblotting demonstrated an 85-kDa band of ClC-5 in the kidney and ClC-5 transfected cells. Immunocytochemistry revealed significant labeling of ClC-5 in brush-border membrane and subapical intracellular vesicles of the proximal tubule. In addition, apical and cytoplasmic staining was observed in the type A intercalated cells in the cortical collecting duct. In contrast, the staining was minimal in the outer and inner medullary collecting ducts and the thick ascending limb. Western blotting of vesicles immunoisolated by the ClC-5 antibody showed the presence of H+-ATPase, strongly indicating that these two proteins were present in the same membranes. Double labeling with antibodies against ClC-5 and H+-ATPase and analysis by confocal images showed that ClC-5 and H+-ATPase colocalized in these ClC-5-positive cells. These findings suggest that ClC-5 might be involved in the endocytosis and/or the H+ secretion in the proximal tubule cells and the cortical collecting duct type A intercalated cells in mouse kidney.

Rapid gating and anion permeability of an intracellular aquaporin

Aquaporin (AQP) water-channel proteins are freely permeated by water but not by ions or charged solutes. Although mammalian aquaporins were believed to be located in plasma membranes, rat AQP6 is restricted to intracellular vesicles in renal epithelia. Here we show that AQP6 is functionally distinct from other known aquaporins. When expressed in Xenopus laevis oocytes, AQP6 exhibits low basal water permeability; however, when treated with the known water channel inhibitor, Hg2+, the water permeability of AQP6 oocytes rapidly rises up to tenfold and is accompanied by ion conductance. AQP6 colocalizes with H+-ATPase in intracellular vesicles of acid-secreting alpha-intercalated cells in renal collecting duct. At pH less than 5.5, anion conductance is rapidly and reversibly activated in AQP6 oocytes. Site-directed mutation of lysine to glutamate at position 72 in the cytoplasmic mouth of the pore changes the cation/anion selectivity, but leaves low pH activation intact. Our results demonstrate unusual biophysical properties of an aquaporin, and indicate that anion-channel function may now be explored in a protein with known structure.

High-resolution immunogold cytochemistry indicates that AQP4 is concentrated along the basal membrane of parietal cell in rat stomach

Gastric parietal cells secrete hydrochloric acid in stomach. Because the secreted HCl solution is isotonic with the plasma fluid, it should accompany the water transport across the membranes of parietal cells. Aquaporins (AQPs) are water channel proteins that play the central role in the cellular handling of water in various mammalian tissues. Using immunocytochemistry, we found that AQP4 was expressed only in parietal cells of rat gastric mucosa. Immunogold electron microscopy study further demonstrated that AQP4 was mostly localized at the basal membrane of parietal cells. In the basal membrane, AQP4 was prominently enriched on the portion contacting with the basement membrane surrounding gastric glands. These results suggest that the contact between basement membrane and basal membrane may generate the signal involved in the targeting of AQP4 in gastric parietal cells.

Lymphoproliferative syndrome with autoimmunity: A possible genetic basis for dominant expression of the clinical manifestations

Fas (CD95/Apo-1) mutations were previously reported as the genetic defect responsible for human lymphoproliferative syndrome associated with autoimmune manifestations (also known as autoimmune lymphoproliferative syndrome or Canale-Smith syndrome). We have identified 14 new heterozygous Fas mutations. Analysis of patients and families allow us to further dissect this syndrome with regards to the relationship between Fas mutations, inheritance pattern, and phenotype as observed on long-term follow-up. In vitro studies show that lymphocytes from all Fas mutant carriers exhibit a Fas-antibody-induced apoptosis defect. However, among the 8 inherited mutations, 4 of 4 Fas missense mutations were associated with high clinical penetrance, whereas 3 of 4 mutations leading to a truncated Fas product were associated with variable clinical penetrance. This suggests that a second defect, in another yet undefined factor involved in apoptosis and/or lymphoproliferation control, is necessary to induce full clinical expression of the disease. These results also indicate that the currently available antibody-mediated in vitro apoptosis assay does not necessarily reflect the in vivo ability of abnormal Fas molecules to trigger lymphocyte death. In addition, we found that lymphoproliferative manifestations resolved with age, whereas immunological disorders [ie, hypergammaglobulinemia and detection of TcR alphabeta(+) CD4(-) CD8(-) lymphocytes] persisted. This observation suggests that Fas-mediated apoptosis plays a more important role in lymphocyte homeostasis in early childhood than later on in life.

Relationship between urinary albumin excretion, body composition, and hyperinsulinemia in normotensive glucose-tolerant adults

OBJECTIVE

Elevated urinary albumin excretion (UAE) has been associated with insulin resistance and is suggested to be elevated in prediabetic individuals. Upper body obesity, especially visceral obesity, predicts insulin resistance and development of type 2 diabetes. We examined whether UAE clusters with obesity-associated insulin resistance traits in healthy glucose-tolerant normotensive subjects.

RESEARCH DESIGN AND METHODS

There were 49 volunteers with a wide range of body fat and body fat distribution studied. All had normal blood pressure and glucose tolerance and were maintained on a controlled diet for 2 weeks. UAE was assessed from three overnight urine collections, and body composition was assessed by whole-body dual-energy X-ray absorptiometry scanning and abdominal computed tomography scanning.

RESULTS

Fasting insulin and insulin responses to oral glucose were significantly increased in obese subjects, who also tended to have more dyslipidemia, greater blood pressure, and more visceral fat than lean subjects. These differences were more apparent in upper body obese subjects. UAE was normal in obese and upper body obese subjects and not different from that of lean subjects. UAE ranged from 0.3 to 8.3 micrograms/min in lean subjects and from 0.2 to 7.2 micrograms/min in obese subjects. UAE was not significantly correlated with body composition, plasma insulin, glucose, or lipids.

CONCLUSIONS

Obese subjects (even upper body obese subjects) with increased visceral and total body fat, high plasma insulin and triglycerides, and low HDL cholesterol concentrations do not have elevated UAE. This suggests that UAE is not closely associated with these characteristics and implies a later onset of abnormal albuminuria in the course of the insulin resistance syndrome.

Reduced abundance of aquaporins in rats with bilateral ischemia-induced acute renal failure: prevention by alpha-MSH

We examined the effect of temporary renal ischemia (30 min or 60 min) and reperfusion (1 day or 5 days) on the expression of renal aquaporins (AQPs) and urinary concentration in rats with bilateral ischemia-induced acute renal failure (ARF). Next, we tested whether reducing ischemia/reperfusion (I/R) injury by treatment with alpha-melanocyte stimulating hormone (alpha-MSH) affects the expression of AQPs and urine output. Rats with ARF showed significant renal insufficiency, and urinary concentration was markedly impaired. In rats with mild ischemic injury (30 min), urine output increased significantly to a maximum at 48 h, and then nearly normalized within 5 days. Consistent with this, semiquantitative immunoblotting revealed that kidney AQP1 and AQP2 abundance was significantly decreased after 24 h to 30 +/- 5% and 40 +/- 11% (n = 8) of controls (n = 9), respectively (P < 0.05). Five days after ischemia, AQP2 abundance was not significantly decreased and urine output was normalized. In contrast, severe ischemic injury (60 min) resulted in a marked reduction in urine output at 24 h, despite a significant decrease in urine osmolality and solute-free water reabsorption, T(c)H(2)O. AQP1 and AQP2 abundance was markedly decreased to 51 +/- 5% and 31 +/- 9% (n = 10) of controls (n = 8) at 24 h (P < 0.05). After 5 days, the rats developed gradually severe polyuria and had very low AQP2 and AQP1 levels [11 +/- 4% and 6 +/- 2% (n = 5) of controls (n = 8), respectively; P < 0.05]. A similar reduction was observed for AQP3. The reduction in AQP expression in the proximal tubule and inner medullary collecting duct was confirmed by immunocytochemistry. Next, we found that intravenous alpha-MSH treatment of rats with ARF significantly reduced the ischemia-induced downregulation of renal AQPs and reduced the polyuria. In conclusion, the I/R injury is associated with markedly reduced expression of the collecting duct and proximal tubule AQPs, in association with an impairment of urinary concentration. Moreover, alpha-MSH treatment significantly prevented the reduction in expression of AQPs and renal functional defects. Thus decreased AQP expression is likely to contribute to the impairment in urinary concentration in the postischemic period.

Heterotetrameric composition of aquaporin-4 water channels

Aquaporin (AQP) water channel proteins are tetrameric assemblies of individually active approximately 30 kDa subunits. AQP4 is the predominant water channel protein in brain, but immunoblotting of native tissues has previously yielded multiple poorly resolved bands. AQP4 is known to encode two distinct mRNAs with different translation initiating methionines, M1 or M23. Using SDS-PAGE urea gels and immunoblotting with anti-peptide antibodies, four polypeptides were identified in brain and multiple other rat tissues with the following levels of expression: 32 kDa > 34 kDa > 36 kDa > 38 kDa. The 34 and 38 kDa polypeptides react with an antibody specific for the N-terminus of the M1 isoform, and 32 and 36 kDa correspond to the shorter M23 isoform. Immunogold electron microscopic studies with rat cerebellum cryosections demonstrated that the 34 kDa polypeptide colocalizes in perivascular astrocyte endfeet where the 32 kDa polypeptide is abundantly expressed. Velocity sedimentation, cross-linking, and immunoprecipitation analyses of detergent-solubilized rat brain revealed that the 32 and 34 kDa polypeptides reside within heterotetramers. Immunoprecipitation of AQP4 expressed in Xenopus laevis oocytes demonstrated that heterotetramer formation reflects the relative expression levels of the 32 and 34 kDa polypeptides; however, tetramers containing different compositions of the two polypeptides exhibit similar water permeabilities. These studies demonstrate that AQP4 heterotetramers are formed from two overlapping polypeptides and indicate that the 22-amino acid sequence at the N-terminus of the 34 kDa polypeptide does not influence water permeability but may contribute to membrane trafficking or assembly of arrays.

Altered expression of Na transporters NHE-3, NaPi-II, Na-K-ATPase, BSC-1, and TSC in CRF rat kidneys

In chronic renal failure (CRF), reduction in renal mass leads to an increase in the filtration rates of the remaining nephrons and increased excretion of sodium per nephron. To address the mechanisms involved in the increased sodium excretion, we determined the total kidney levels and the densities per nephron of the major renal NaCl transporters in rats with experimental CRF. Two weeks after 5/6 nephrectomy (reducing the total number of nephrons to approximately 24 +/- 8%), the rats were azotemic and displayed increased Na excretion. Semiquantitative immunoblotting revealed significant reduction in the total kidney levels of the proximal tubule Na transporters NHE-3 (48% of control), NaPi-II (13%), and Na-K-ATPase (30%). However, the densities per nephron of NHE-3, NaPi-II, and Na-K-ATPase were not significantly altered in remnant kidneys, despite the extensive hypertrophy of remaining nephrons. Immunocytochemistry confirmed the reduction in NHE-3 and Na-K-ATPase labeling densities in the proximal tubule. In contrast, there was no significant reduction in the total kidney levels of the thick ascending limb and distal convoluted tubule NaCl transporters BSC-1 and TSC, respectively. This corresponded to a 3.6 and 2.5-fold increase in densities per nephron, respectively (confirmed by immunocytochemistry). In conclusion, in this rat CRF model: 1) increased fractional sodium excretion is associated with altered expression of proximal tubule Na transporter expression (NHE-3, NaPi-II, and Na-K-ATPase), consistent with glomerulotubular imbalance in the face of increased single-nephron glomerular filtration rate; and 2) compensatory increases in BSC-1 and TSC expression per nephron occur in distal segments.

Randomised trial comparing expectant with medical management for first trimester miscarriages

OBJECTIVE

To compare the efficacy of antiprogesterone (mifepristone) in combination with a synthetic prostaglandin E1 analogue (misoprostol) for outpatient treatment of miscarriages.

PARTICIPANTS

One hundred and twenty-two women with first trimester miscarriages.

METHODS

The women were randomised to treatment with mifepristone 400 mg orally followed by a single oral dose of 400 microg misoprostol 48 hours later (n = 60) or expectant management (n = 62). Women were re-evaluated five days later. If retained intrauterine products of conception were found with an antero-posterior diameter above 15 mm on transvaginal ultrasound, surgical evacuation was performed.

RESULTS

Eighty-two percent of the women randomised to pharmacological treatment and 76% of those randomised to expectant management had an empty uterine cavity after five days. Convalescence time was 1.8 days longer for women randomised to pharmacological treatment. Pain, bleeding, complications, and satisfaction with the treatment did not differ between the groups.

CONCLUSIONS

Most cases of spontaneous incomplete miscarriage will become a complete miscarriage without intervention. This study shows that outpatient treatment with a combination of antiprogesterone and a prostaglandin E1 analogue did not increase the rate of complete miscarriage, compared with expectancy alone, by a clinical important degree.

Decreased abundance of collecting duct aquaporins in post-ischemic renal failure in rats

Increased urine flow is often a feature of mild to moderate acute renal failure. This study examines the possible role of dysregulation of collecting duct aquaporins as a factor in this increase. In rats, the left renal pedicle was clamped for 45 min followed by contralateral nephrectomy. Control rats were identical except that the renal pedicle was not clamped. Rats were sacrificed and the kidneys were homogenized at various time points after release of the clamp for semiquantitative immunoblotting of collecting duct aquaporins, as well as the thick ascending limb Na-K-2Cl cotransporter and the proximal tubule water channel, aquaporin-1. Urinary flow rate was significantly increased 18 h after the ischemic insult and remained increased through 72 h. Whole kidney aquaporin-2 protein abundance was 45% of controls at 18 h, 55% of controls at 36 h, and returned to normal 72 h after ischemia. Whole kidney aquaporin-3 protein abundance was 37% of controls at 18 h, 13% of controls at 36 h, and 45% of controls at 72 h. The decline in aquaporin-2 and -3 was confirmed by immunocytochemistry. Abundance of the thick ascending limb Na-K-2Cl cotransporter protein was not significantly decreased. Aquaporin-1 protein abundance was not significantly decreased at 18 h after the ischemic insult, but was significantly reduced after 36 h. Thus, the post-ischemic state is associated with decreased levels of the collecting duct aquaporins, coinciding with an increase in water excretion. It is concluded that decreased aquaporin protein abundance in collecting duct cells is a contributing factor in the increased urine flow seen in moderate post-ischernic acute renal failure.

Cyclooxygenase inhibitors increase Na-K-2Cl cotransporter abundance in thick ascending limb of Henle's loop

Cyclooxygenase inhibitors, such as indomethacin and diclofenac, have well-described effects to enhance renal water reabsorption and urinary concentrating ability. Concentrating ability is regulated in part at the level of the thick ascending limb of Henle's loop, where active NaCl absorption drives the countercurrent multiplication mechanism. We used semiquantitative immunoblotting to test the effects of indomethacin and diclofenac, given over a 48-h period, on the expression levels of the ion transporters responsible for active NaCl transport in the thick ascending limb. Both agents strongly increased the expression level of the apical Na-K-2Cl cotransporter in both outer medulla and cortex. Neither agent significantly altered outer medullary expression levels of other thick ascending limb proteins, namely, the type 3 Na/H exchanger (NHE-3), Tamm-Horsfall protein, or alpha1- or beta1-subunits of the Na-K-ATPase. Administration of the EP3-selective PGE(2) analog, misoprostol, to indomethacin-treated rats reversed the stimulatory effect of indomethacin on Na-K-2Cl cotransporter expression. We conclude that cyclooxygenase inhibitors enhance urinary concentrating ability in part through effects to increase Na-K-2Cl cotransporter expression in the thick ascending limb of Henle's loop. This action is most likely due to elimination of an EP3-receptor-mediated tonic inhibitory effect of PGE(2) on cAMP production.

Epidemiology of juvenile chronic arthritis: risk dependent on sibship, parental income, and housing

OBJECTIVE

We studied the socioeconomic background of children with juvenile chronic arthritis (JCA) diagnosed during the years 1988-91 in Denmark. The working hypothesis is that JCA may be triggered by one or several different infectious agents and that the amount of exposure to infectious agents in infancy and childhood affects the risk of JCA.

METHODS

In this case-control study, we investigated socioeconomic variables prior to disease onset from national registers, primarily the Fertility Database of Statistics Denmark, in a national cohort of all 220 known cases of JCA fulfilling the EULAR criteria incident during the years 1988-91, identified from national and local diagnosis registers. There were 4 controls per case, matched for sex, age, and county of residence. Socioeconomic variables as risk factors were quantified by odds ratios, which are equivalent to relative risks of contracting JCA if exposed to a risk factor.

RESULTS

Three socioeconomic variables were significantly and mutually independently associated with the risk of developing JCA during the following year. An only child had a risk of JCA 1.6 times that of a child with siblings. Children whose parents had a high income had a relative risk of 1.9. Children living in an urban flat had a risk 2.7 times that of children living on a farm. We found no space-time clustering of cases and no cyclical variations of incidence rates.

CONCLUSION

The absence of clustering and of seasonal variation does not support a theory of triggering by infection. The hitherto unreported effects of the socioeconomic variables on the risk of JCA are of the same order of magnitude as reported for certain HLA alleles. Our findings do not lend full support to either of the 2 mechanisms, that growing up under either hygienic or unhygienic conditions increases the risk of JCA, and lack an obvious biological explanation.