On multistability behavior of unstable dissipative systems.

We present dissipative systems with unstable dynamics called the unstable dissipative systems which are capable of generating a multi-stable behavior, i.e., depending on its initial condition, the trajectory of the system converges to a specific attractor. Piecewise linear (PWL) systems are generated based on unstable dissipative systems, whose main attribute when they are switched is the generation of chaotic trajectories with multiple wings or scrolls. For this PWL system, a structure is proposed where both the linear part and the switching function depend on two parameters. We show the range of values of such parameters where the PWL system presents a multistable behavior and trajectories with multiscrolls.

Estudio del nivel de concordancia entre los diagnósticos prequirúrgico y artroscópico de lesiones meniscales asociadas a lesiones del ligamento cruzado anterior / Concordance between preoperatory diagnosis and arthroscopy findings of meniscal lesions associated to anterior cruciate ligament injury

Introducción: Las lesiones ligamentarias de la rodilla son comunes durante la segunda y tercera décadas de vida, su diagnóstico clínico es difícil ya que puede diferir con el diagnóstico definitivo. El objetivo es determinar la concordancia entre el diagnóstico preoperatorio-diagnóstico postoperatorio y entre la lesión meniscal sospechada-lesión meniscal encontrada, en pacientes con lesión del ligamento cruzado anterior. Material y métodos: Estudio transversal. En 29 pacientes con lesión del ligamento cruzado anterior a los cuales se realizó artroscopía. Las variables fueron edad, género, lado afectado, diagnóstico preoperatorio, diagnóstico postoperatorio, lesión meniscal sospechada, lesión meniscal encontrada. La estadística utilizada fue descriptiva, para la concordancia se usó índice de Kappa de Cohen. Resultados: Fueron 29 pacientes, 23 (79.3%) hombres y 6 (20.7%) mujeres, la edad promedio: 39.04 (15-50) ± 13.19 años, lado afectado derecho 69% e izquierdo 31%; el diagnóstico preoperatorio en 22 (75%) pacientes fue LLCA aislada, LLCA + menisco medial 6 (20.7%), LLCA + menisco lateral 1 (3.4%) y el diagnóstico artroscópico fue en 20 (68.96%) sin lesión meniscal, 7 (24.1%) lesión en menisco medial, 2 (6.9%) en menisco lateral, con una concordancia baja (Kappa 0.2), la concordancia diagnóstica preoperatoria intraobservador fue perfecta (Kappa 1.0); y la concordancia entre el diagnóstico de la lesión meniscal preoperatoria y de la lesión meniscal artroscópica fue baja (Kappa 0.2). Conclusiones: La concordancia entre el diagnóstico clínico-radiológico y el diagnóstico artroscópico en lesiones del LCA con asociación de lesión meniscal es baja, lo cual se tiene que tener en cuenta en la realización del diagnóstico inicial y en el tratamiento artroscópico de los pacientes.

Introduction: Ligament injuries of the knee joint are common during the second and third decades of life, clinical and radiological diagnosis presents difficulties since the surgical findings may differ significantly. The objective is to determine correlation between clinical-radiologic and arthroscopic diagnosis in patients with injury of the anterior cruciate ligament (ACL) and meniscal lesions. Material and methods: Cross-sectional study held in 29 patients with ACL injury associated to meniscal lesions treated arthroscopically. Variables were age, gender, affected side, preoperative and postoperative diagnosis, type and location of meniscal injury; descriptive statistics and Cohen Kappa for concordance were used. Results: There were 29 patients, 23 (79.3%) men and 6 (20.7%) women, mean age 39.04 (15-50) ± 13.19 years; right side was affected in 69% and left in 31%; 19% had not meniscal lesion, 17.2% had injury in anterior horn, 10.3% in posterior horn and 6.9% in the body. The concordance between preoperative and artroscopic diagnosis was: Kappa 0.2; intraboservador was Kappa 1.0; between suspected meniscal injury and arthroscopic findings was: Kappa 0.2. Conclusions: The concordance between the clinical-radiological and arthroscopic diagnosis in patients with ACL injuries and meniscal injury associated is low, which has to be considered in the initial review and the arthroscopic treatment of patients.

[Concordance between preoperatory diagnosis and arthroscopy findings of meniscal lesions associated to anterior cruciate ligament injury]. / Estudio del nivel de concordancia entre los diagnósticos prequirúrgico y artroscópico de lesiones meniscales asociadas a lesiones del ligamento cruzado anterior.

INTRODUCTION: Ligament injuries of the knee joint are common during the second and third decades of life, clinical and radiological diagnosis presents difficulties since the surgical findings may differ significantly. The objective is to determine correlation between clinical-radiologic and arthroscopic diagnosis in patients with injury of the anterior cruciate ligament (ACL) and meniscal lesions. MATERIAL AND METHODS: Cross-sectional study held in 29 patients with ACL injury associated to meniscal lesions treated arthroscopically. Variables were age, gender, affected side, preoperative and postoperative diagnosis, type and location of meniscal injury; descriptive statistics and Cohen Kappa for concordance were used. RESULTS: There were 29 patients, 23 (79.3%) men and 6 (20.7%) women, mean age 39.04 (15-50) ± 13.19 years; right side was affected in 69% and left in 31%; 19% had not meniscal lesion, 17.2% had injury in anterior horn, 10.3% in posterior horn and 6.9% in the body. The concordance between preoperative and artroscopic diagnosis was: Kappa 0.2; intraboservador was Kappa 1.0; between suspected meniscal injury and arthroscopic findings was: Kappa 0.2. CONCLUSIONS: The concordance between the clinical-radiological and arthroscopic diagnosis in patients with ACL injuries and meniscal injury associated is low, which has to be considered in the initial review and the arthroscopic treatment of patients.

INTRODUCCIÓN: Las lesiones ligamentarias de la rodilla son comunes durante la segunda y tercera décadas de vida, su diagnóstico clínico es difícil ya que puede diferir con el diagnóstico definitivo. El objetivo es determinar la concordancia entre el diagnóstico preoperatorio-diagnóstico postoperatorio y entre la lesión meniscal sospechada-lesión meniscal encontrada, en pacientes con lesión del ligamento cruzado anterior. MATERIAL Y MÉTODOS: Estudio transversal. En 29 pacientes con lesión del ligamento cruzado anterior a los cuales se realizó artroscopía. Las variables fueron edad, género, lado afectado, diagnóstico preoperatorio, diagnóstico postoperatorio, lesión meniscal sospechada, lesión meniscal encontrada. La estadística utilizada fue descriptiva, para la concordancia se usó índice de Kappa de Cohen. RESULTADOS: Fueron 29 pacientes, 23 (79.3%) hombres y 6 (20.7%) mujeres, la edad promedio: 39.04 (15-50) ± 13.19 años, lado afectado derecho 69% e izquierdo 31%; el diagnóstico preoperatorio en 22 (75%) pacientes fue LLCA aislada, LLCA + menisco medial 6 (20.7%), LLCA + menisco lateral 1 (3.4%) y el diagnóstico artroscópico fue en 20 (68.96%) sin lesión meniscal, 7 (24.1%) lesión en menisco medial, 2 (6.9%) en menisco lateral, con una concordancia baja (Kappa 0.2), la concordancia diagnóstica preoperatoria intraobservador fue perfecta (Kappa 1.0); y la concordancia entre el diagnóstico de la lesión meniscal preoperatoria y de la lesión meniscal artroscópica fue baja (Kappa 0.2). CONCLUSIONES: La concordancia entre el diagnóstico clínico-radiológico y el diagnóstico artroscópico en lesiones del LCA con asociación de lesión meniscal es baja, lo cual se tiene que tener en cuenta en la realización del diagnóstico inicial y en el tratamiento artroscópico de los pacientes.

Reducing exposure to long days from 75 to 30 days of extra-light treatment does not decrease the capacity of male goats to stimulate ovulatory activity in seasonally anovulatory females.

The response of male goats exposed to different durations of long days (LD) during an extra-light treatment in autumn-winter, and their ability to induce ovulations in seasonally anovulatory goats were investigated in 2 experiments. In experiment 1, control males were exposed to natural photoperiod (n = 5), whereas 4 additional groups (n = 5/group) were exposed to 16 h of light per d during 75, 45, 30, or 15 d of LD. In the 4 groups, photoperiodic treatments ended on January 15th. Plasma concentrations of testosterone were determined in blood samples obtained once a week from October 15th to May 30th. The rise of testosterone levels occurred earlier in males from the 75-LD and 45-LD groups than in those from the 30-LD, 15-LD, and control groups (P < 0.05). In addition, the time during which levels of testosterone remained >5 ng/mL was longer in males from the 75-LD and 45-LD than in those from the 30-LD and 15-LD groups (P < 0.05). In experiment 2, a group of anovulatory goats (n = 13) was isolated from males, while 3 additional groups were put in contact during 15 d with males previously exposed to 75, 45, or 30 days of LD (n = 25, 27, and 26 females/group, respectively and n = 3 males per group). The proportion of goats that ovulated was higher in the 3 groups in contact with the photo-stimulated males (range: 88%-92%) than in the group isolated from them (0%; P < 0.05). The proportion of pregnant females did not differ between the 3 groups of does in contact with photo-stimulated males (range: 78%-92%; P > 0.05). We conclude that, in our experimental conditions, a photoperiodic treatment as short as 30 d of LD during autumn-winter, stimulated testosterone secretion of bucks during their period of sexual rest and rendered them able to induce ovulations in seasonal anestrous goats and to obtain pregnancies in these females.

Sexually active bucks are able to stimulate three successive groups of females per day with a 4-hour period of contact.

Bucks rendered sexually active by a photoperiod treatment of long days can induce fertile ovulation in a group of goats with only 4 h of contact daily with a male:female ratio of 1:10. Here we tested whether such bucks could induce fertile ovulations when stimulating successively three different groups of anovulatory goats when interacting 4 h per day during 15 consecutive days. Control males (n=3) were introduced in the control group (n=25) of does at 8:00 h and were removed at 12:00 h. Experimental males (n=3) were in contact with the experimental groups of does: from 8:00 h to 12:00 h with a first group (n=27), from 12:00 h to 16:00 h with a second group (n=26) and with a third one (n=27) from 16:00 h to 20:00 h. Bucks were then placed until next day in another pen. Both in the control and the experimental groups, more than 85% of females ovulated, and the proportions did not differ between the control and experimental groups (P≥0.67) or between the three experimental groups (P≥0.67). Moreover, the ovulation rate did not differ significantly between the control and the experimental females nor between the three experimental groups. Bucks were able to fertilize more than 72% of does independently of the number of females they were exposed to (P≥0.17). Finally, more than 58% of females kidded and fertility did not differ between the control and experimental groups (P=1) nor among experimental groups (P≥0.77). We conclude that sexually active bucks are able to induce fertile ovulation in three successive groups of anovulatory goats even when the period of contact between sexes is reduced to 4 h per day.

Podocyte vascular endothelial growth factor (Vegf164) overexpression causes severe nodular glomerulosclerosis in a mouse model of type 1 diabetes.

AIMS/HYPOTHESIS: The pathogenic role of excessive vascular endothelial growth factor (VEGF)-A in diabetic nephropathy has not been defined. We sought to test whether increased podocyte VEGF-A signalling determines the severity of diabetic glomerulopathy. METHODS: Podocyte-specific, doxycycline-inducible Vegf164 (the most abundant Vegfa isoform) overexpressing adult transgenic mice were made diabetic with low doses of streptozotocin and examined 12 weeks after onset of diabetes. We studied diabetic and non-diabetic transgenic mice fed a standard or doxycycline-containing diet. VEGF-A and albuminuria were measured by ELISA, creatinine was measured by HPLC, renal morphology was examined by light and electron microscopy, and gene expression was assessed by quantitative PCR, immunoblotting and immunohistochemistry. RESULTS: Podocyte Vegf164 overexpression in our mouse model of diabetes resulted in advanced diabetic glomerulopathy, characterised by Kimmelstiel-Wilson-like nodular glomerulosclerosis, microaneurysms, mesangiolysis, glomerular basement membrane thickening, podocyte effacement and massive proteinuria associated with hyperfiltration. It also led to increased VEGF receptor 2 and semaphorin3a levels, as well as nephrin and matrix metalloproteinase-2 downregulation, whereas circulating VEGF-A levels were similar to those in control diabetic mice. CONCLUSIONS/INTERPRETATION: Collectively, these data demonstrate that increased podocyte Vegf164 signalling dramatically worsens diabetic nephropathy in a streptozotocin-induced mouse model of diabetes, resulting in nodular glomerulosclerosis and massive proteinuria. This suggests that local rather than systemic VEGF-A levels determine the severity of diabetic nephropathy and that semaphorin3a signalling and matrix metalloproteinase-2 dysregulation are mechanistically involved in severe diabetic glomerulopathy.

Torasemide significantly reduces thiazide-induced potassium and magnesium loss despite supra-additive natriuresis.

BACKGROUND: Resistance to high-dose loop diuretics can be overcome either by co-administration with thiazides or by treatment with medium-dose loop diuretics combined with thiazides. Combination therapy has been proven to be superior to high-dose loop diuretic monotherapy for cardiac and renal edema. However, such a strongly efficacious short-term regimen is often complicated by undesired effects, including circulatory collapse and electrolyte disturbances. The question of whether the loop diuretic/thiazide combinations are efficacious and safe when conventional doses are combined has not yet been answered. METHODS: The effects of hydrochlorothiazide (HCT) and torasemide (TO) given alone on the excretion of Na+, Cl-, K+, Mg2+, and Ca2+ were compared with the effects of combined administration of the diuretics in 12 healthy volunteers. RESULTS: The co-administration of HCT (25 mg) with TO (5 or 10 mg) strongly increased Na+ excretion. However, the combination significantly reduced K+ and Mg2+ excretion. The K+-sparing effect of the HCT/TO combination was shown to be due to a significant reduction in the HCT-induced increase in fractional K+ excretion by the loop diuretic. Total excretion of Ca2+ relative to Na+ excretion was less with the HCT/TO combination than with TO given alone. CONCLUSION: The enhancement of desired NaCl excretion by the HCT/TO combination with significant reduction of undesired loss of K+ and Mg2+ meets clinical requirements but has to be validated in long-term clinical trials.

Cross-cultural evaluation of two drinking assessment instruments: alcohol timeline followback and inventory of drinking situations.

This article describes the psychometric characteristics of two major assessment instruments used in a World Health Organization (WHO) clinical trial: (a) Alcohol Timeline Followback (TLFB, which assesses daily drinking patterns), and (b) Inventory of Drinking Situations (IDS, which assesses antecedents to "heavy" drinking). Clients (N = 308) were outpatient alcohol abusers from four countries (Australia, Canada, Mexico, and Sweden). Generally, the Alcohol TLFB and IDS were shown to be reliable and valid with outpatient alcohol abusers in four countries, and in three languages. These results suggest that the Alcohol TLFB and the IDS can be used in clinical and research settings with Swedish-, Spanish-, and English-speaking alcohol abusers.

The distal convoluted tubule of rabbit kidney does not express a functional sodium channel.

We sought to assess whether the distal convoluted tubule (DCT) segment of the rabbit nephron expresses a functional epithelial sodium channel. First, the transepithelial voltage (V(te), lumen vs. bath) was measured in isolated perfused DCT segments (assessed separately in the upstream half and the downstream half of the DCT). V(te) was zero and not affected by amiloride or barium in the upstream DCT. V(te) was sometimes negative in the downstream DCT and depolarized by amiloride and hyperpolarized by barium, suggesting inclusion of connecting tubule (CNT) cells. To determine expression of epithelial sodium channel (ENaC) mRNA subunits by the upstream DCT, rabbit alpha-, beta-, and gamma-ENaC cDNA fragments were cloned and primers were selected for single-nephron RT-PCR analysis. Although alpha-ENaC was expressed by the DCT, beta- and gamma-ENaC were not detected in the DCT. In contrast, the CNT, CCD, and outer medullary collecting duct (OMCD) expressed all three subunits. Nedd4 was also not detected in the DCT but was expressed by the CNT, CCD, and OMCD. When upstream DCT fragments were grown to confluent monolayers in primary culture, the epithelia exhibited negative voltages and high transepithelial resistances and expressed mRNA for all three ENaC subunits as well as for Nedd4. The absence of a negative voltage and failure to detect transcript for beta- and gamma-ENaC and Nedd4 in the native rabbit DCT suggest that the sodium channel is not a significant pathway for sodium absorption by this segment. The phenotype conversion observed when DCT cells are grown in culture does not rule out the possibility that there may be conditions in which the DCT in the intact kidney expresses sodium channel activity. The results are consistent with the notion that DCT sodium transport is predominantly, if not exclusively, electroneutral.

Defective processing and expression of thiazide-sensitive Na-Cl cotransporter as a cause of Gitelman's syndrome.

Gitelman's syndrome is an autosomal recessive disorder of salt wasting and hypokalemia caused by mutations in the thiazide-sensitive Na-Cl cotransporter. To investigate the pathogenesis of Gitelman's syndrome, eight disease mutations were introduced into the mouse thiazide-sensitive Na-Cl cotransporter and studied by functional expression in Xenopus oocytes. Sodium uptake into oocytes that expressed the wild-type clone was more than sevenfold greater than uptake into control oocytes. Uptake into oocytes that expressed the mutated transporters was not different from control. Hydrochlorothiazide reduced Na uptake by oocytes expressing the wild-type gene to control values but had no effect on oocytes expressing the mutant clones. Western blots of oocytes injected with the wild-type clone showed bands representing glycosylated (125 kDa) and unglycosylated (110 kDa) forms of the transport protein. Immunoblot of oocytes expressing the mutated clones showed only the unglycosylated protein, indicating that protein processing was disrupted. Immunocytochemistry with an antibody against the transport protein showed intense membrane staining of oocytes expressing the wild-type protein. Membrane staining was completely absent from oocytes expressing mNCC(R948X); instead, diffuse cytoplasmic staining was evident. In summary, the results show that several mutations that cause Gitelman's syndrome are nonfunctional because the mutant thiazide-sensitive Na-Cl cotransporter is not processed normally, probably activating the "quality control" mechanism of the endoplasmic reticulum.

Tratamiento combinado con metotrexate sistémico y resección histeroscópica en un caso de embarazo ectópico cervical / Combined treatment with sistemic methotrexate and hysteroscopic resection in a case of cervical ectopic pregnancy

El embarazo ectópico cervical es un cuadro de muy baja frecuencia y sumamente peligroso por la posibilidad de penetración de la pared por el trofoblasto hacia las arterias uterinas con compromiso de la vida de la paciente por hemorragia incontrolable y de su fertilidad futura cuando el único recurso terapéutico es la histerectomía. En la actualidad y gracias a la disponibilidad de recursos que permiten un diagnóstico precoz, son las técnicas no quirúrgicas las que constituyen la primera línea terapéutica. Se presenta el caso de una paciente de 30 años con diagnóstico de esterilidad primaria que ingresa al programa de ART, se realiza un ICSI por factor masculino que resulta en un embarazo bioquímico. Dos ciclos más tarde y durante la evaluación previa al comienzo de un nuevo ciclo luego de tratamiento con acetato de noretisterona por spotting se realiza el diagnóstico ecográfico de embarazo ectópico cervical. Fue tratada con metotrexate sistémico y al presentar sangrado se procedió a su resección por vía histeroscópica con éxito

Tratamiento combinado con metotrexate sistémico y resección histeroscópica en un caso de embarazo ectópico cervical / Combined treatment with sistemic methotrexate and hysteroscopic resection in a case of cervical ectopic pregnancy

El embarazo ectópico cervical es un cuadro de muy baja frecuencia y sumamente peligroso por la posibilidad de penetración de la pared por el trofoblasto hacia las arterias uterinas con compromiso de la vida de la paciente por hemorragia incontrolable y de su fertilidad futura cuando el único recurso terapéutico es la histerectomía. En la actualidad y gracias a la disponibilidad de recursos que permiten un diagnóstico precoz, son las técnicas no quirúrgicas las que constituyen la primera línea terapéutica. Se presenta el caso de una paciente de 30 años con diagnóstico de esterilidad primaria que ingresa al programa de ART, se realiza un ICSI por factor masculino que resulta en un embarazo bioquímico. Dos ciclos más tarde y durante la evaluación previa al comienzo de un nuevo ciclo luego de tratamiento con acetato de noretisterona por spotting se realiza el diagnóstico ecográfico de embarazo ectópico cervical. Fue tratada con metotrexate sistémico y al presentar sangrado se procedió a su resección por vía histeroscópica con éxito (AU)

Intrarenal distribution of the colonic H,K-ATPase mRNA in rabbit.

BACKGROUND: Evidence suggests that the colonic H,K-ATPase isoform is expressed in the kidney and that a mRNA species highly homologous to the rat and guinea pig HKalpha2 is expressed in the cortical collecting duct (CCD) of the rabbit. The goals of this study were to determine if this mRNA is the rabbit homologue of HKalpha2 or a novel isoform and to determine intrarenal distribution of the HKalpha2 mRNA in rabbit. METHODS: 5'-RACE and Dye Deoxy Terminator chemistry were used to determine the full-length sequence of the rabbit HKalpha2 mRNA. The intrarenal distribution of HKalpha2 mRNA was determined in microdissected nephron segments, connecting tubule (CNT), and CCD cells isolated by immunodissection, as well as in the three cell types of the CCD. Principal cells and alpha- and beta-intercalated cells were isolated by fluorescence-activated cell sorting. HKalpha2 mRNA levels were determined by quantitative reverse transcription-polymerase chain reaction (RT-PCR) or single-nephron RT-PCR (SN-RTPCR). RESULTS: The full-length sequence of the rabbit kidney HKalpha2 mRNA was determined. This transcript is identical to the one expressed in rabbit distal colon. In microdissected nephron segments, strong HKalpha2 amplicons were present in the CNT, CCD, and outer medullary collecting duct (OMCD), whereas no signal was detected in the proximal tubule, distal convoluted tubule, think ascending limb, and inner medullary collecting duct. Roughly comparable levels of HKalpha2 mRNA were present in all three CCD cell types, and the highest levels were observed in a subpopulation most likely corresponding to CNT cells. CONCLUSIONS: These results suggest that the HKalpha2 mRNA is expressed in rabbit collecting duct is identical in size and sequence to the one expressed in rabbit distal colon. HKalpha2 mRNA in the rabbit kidney is selectively expressed in the CNT, CCD, and OMCD, and all three collecting duct subtypes express its mRNA.

Paracellin-1, a renal tight junction protein required for paracellular Mg2+ resorption.

Epithelia permit selective and regulated flux from apical to basolateral surfaces by transcellular passage through cells or paracellular flux between cells. Tight junctions constitute the barrier to paracellular conductance; however, little is known about the specific molecules that mediate paracellular permeabilities. Renal magnesium ion (Mg2+) resorption occurs predominantly through a paracellular conductance in the thick ascending limb of Henle (TAL). Here, positional cloning has identified a human gene, paracellin-1 (PCLN-1), mutations in which cause renal Mg2+ wasting. PCLN-1 is located in tight junctions of the TAL and is related to the claudin family of tight junction proteins. These findings provide insight into Mg2+ homeostasis, demonstrate the role of a tight junction protein in human disease, and identify an essential component of a selective paracellular conductance.

11Beta-hydroxysteroid dehydrogenase, mineralocorticoid receptor, and thiazide-sensitive Na-Cl cotransporter expression by distal tubules.

Mineralocorticoid hormones regulate salt transport along the distal nephron by binding to intracellular receptors and activating gene transcription. Previous experiments showed that systemic aldosterone infusions stimulate thiazide-sensitive Na and Cl transport by distal convoluted tubule (DCT) cells; this effect could have been direct or secondary to systemic hormonal effects. Aldosterone target tissues express both mineralocorticoid receptors and the metabolic enzyme 11beta-hydroxysteroid dehydrogenase type 2. Mineralocorticoid receptors have been localized to the DCT in some experiments, but not in others. Expression of 11beta-hydroxysteroid dehydrogenase type 2 by DCT cells has not been investigated. The present experiments were designed to test the hypothesis that rat DCT cells are targets of aldosterone action. Patterns of mineralocorticoid receptor, 11beta-hydroxysteroid dehydrogenase, thiazide-sensitive Na-Cl cotransporter, and Na/Ca exchanger expression along the distal tubule were examined. A polyclonal antibody was generated to localize the thiazide-sensitive Na-Cl cotransporter. Thiazide-sensitive Na-Cl cotransporter and 11beta-hydroxysteroid dehydrogenase expression were examined using both in situ hybridization and immunocytochemistry; Na/Ca exchanger and mineralocorticoid receptor expression were examined by immunocytochemistry. The results indicate that 11beta-hydroxysteroid dehydrogenase is expressed by DCT cells, as well as connecting tubule cells and principal cells of the collecting duct; expression levels are low near the junction with the thick ascending limb and rise near the transition to the connecting tubule. Mineralocorticoid receptors are expressed by DCT cells, as well as along the thick ascending limb, connecting tubule, and collecting duct. The results indicate that components of the mineralocorticoid receptor system are expressed by DCT cells, suggesting that these cells are targets of aldosterone action.

Rabbit distal convoluted tubule coexpresses NaCl cotransporter and 11 beta-hydroxysteroid dehydrogenase II mRNA.

BACKGROUND: Although the renal cortical collecting duct (CCD) is a principal target for aldosterone, recent evidence suggests that salt transport by other nephron segments may also be regulated by aldosterone. Electroneutral and thiazide-sensitive NaCl cotransport by the distal convoluted tubule (DCT) of the rat is increased in animals deprived of dietary NaCl. We tested the hypothesis that the DCT of the rabbit is an aldosterone target tissue. METHODS: The single-nephron reverse-transcriptase/polymerase chain reaction (RT-PCR) technique was used to determine mRNA expression of NaCl cotransporter and 11 beta-HSD 2 in dissected nephron segments. The rabbit NaCl cotransporter was first cloned and rabbit-specific primers selected. A micro-assay was developed to assess 11 beta-HSD 2 enzyme activity in 0.5 mm samples of the same nephron segments. RESULTS: NaCl cotransporter was expressed in 0 of 6 proximal tubule (PT), 6 of 6 DCT and 3 of 6 CCD samples, while 11 beta-HSD was found in 0 of 7 PT, 7 of 7 DCT and 9 of 9 CCD samples. Corticosterone was converted to 11-dehydrocorticosterone at a high rate and to a similar extent by both the DCT and CCD, but not the PT. CONCLUSIONS: We conclude that the DCT is a target tissue for the action of aldosterone. Axial heterogeneity of electroneutral (in DCT) and electrogenic (in CCD) Na transporters along the distal nephron may improve sodium recovery in low salt and volume states.