Enhanced expression of epithelial sodium channels in the renal medulla of Dahl S rats.

Inner medullary collecting duct (IMCD) cells from salt-sensitive (S) Dahl rats transport twice as much Na(+) as cells from salt-resistant (R) rats, possibly related to dysregulation of the renal epithelial sodium channel (ENaC). The effect of a high-salt diet on ENaC expression in the inner medulla of S versus R rats has not yet been studied. Young, male S and R rats were placed on a regular-salt (0.3%) or high-salt (8%) diet for 2 or 4 weeks. mRNA and protein expression of ENaC subunits were studied by real-time PCR and immunoblotting. Intracellular distribution of the subunits in the IMCD was evaluated by immunohistochemistry. On regular salt, the abundance of the mRNA of ß and γENaC was higher in the medulla of S rats than R rats. This was associated with a greater protein abundance of 90 kDa γENaC and higher immunoreactivity for both α and γ ENaC. High salt did not affect mRNA abundance in either strain and decreased apical staining of ßENaC in IMCD of R rats. In contrast, high salt did not affect the higher apical localization of αENaC and increased the apical membrane staining for ß and γENaC in the IMCD of S rats. Expression of ENaC subunits is enhanced in the medulla of S vs. R rats on regular salt, and further increased on high salt. The persistent high expression of αENaC and increase in apical localization of ß and γENaC may contribute to greater retention of sodium in S rats on a high-salt diet.

Effects of central sodium on epithelial sodium channels in rat brain.

We evaluated the effects of intracerebroventricular (icv) infusion of Na(+)-rich artificial cerebrospinal fluid (aCSF), with or without the mineralocorticoid receptor (MR) blocker spironolactone, on epithelial Na(+) channel (ENaC) subunits and regulators, such as MR, serum/glucocorticoid-inducible kinase 1, neural precursor cells expressed developmentally downregulated 4-like gene, 11beta-hydroxylase, and aldosterone synthase, in brain regions of Wistar rats. The effects of icv infusion of the amiloride analog benzamil on brain tissue and CSF Na(+) concentration ([Na(+)]) were also assessed. In the choroid plexus and ependyma of the anteroventral third ventricle, ENaC subunits are present in apical and basal membranes. Na(+)-rich aCSF increased beta-ENaC mRNA and immunoreactivity in the choroid plexus and increased alpha- and beta-ENaC immunoreactivities in the ependyma. Na(+)-rich aCSF increased alpha- and beta-ENaC-gold-labeled particles in the microvilli of the choroid plexus and in basolateral membranes of the ependyma. Spironolactone only prevented the increase in beta-ENaC immunoreactivity in the choroid plexus and ependyma. In the supraoptic nucleus, paraventricular nucleus, and subfornical organ, Na(+)-rich aCSF did not affect mRNA expression levels of the studied genes. Benzamil significantly increased CSF [Na(+)] in the control, but not Na(+)-rich, aCSF group. In contrast, benzamil prevented the increase in hypothalamic tissue [Na(+)] by Na(+)-rich aCSF. These results suggest that CSF Na(+) upregulates ENaC expression in the brain epithelia, but not in the neurons of hypothalamic nuclei. ENaC in the choroid plexus and ependyma appear to contribute to regulation of Na(+) homeostasis in the brain.

Autoantibody to heterogeneous nuclear ribonucleoprotein-A2 (RA33) in juvenile idiopathic arthritis: clinical significance.

BACKGROUND: Objective biomarkers are needed for early diagnosis of juvenile idiopathic arthritis (JIA). Anti-A33 antibodies are considered good markers for adult rheumatoid arthritis (RA), but little information is available on their occurrence in JIA. The aim of the present study was therefore to investigate the value of anti-RA33 for diagnosis of JIA (both early and established disease), and its relation to markers of disease activity, and bone resorption. SUBJECTS: This case-control study was conducted on 34 children with JIA. Ten patients with arthritis of short duration (<6 weeks) were included, as undifferentiated arthritis. Forty-four age- and sex- matched healthy children served as controls. Beside evaluation and assessment of disease activity, urinary calcium, serum parathyroid hormone and serum anti-RA33 were measured in included subjects. Joints were examined radiologically and modified Larsen index (LI) was estimated. RESULTS: During follow up, eight of the patients with undifferentiated arthritis were diagnosed as having early JIA. Patients with JIA (early and established cases) had higher anti-RA33 levels than the control group (z = 6.04, 3.95, respectively). A total of 66.7% of the patients were positive for anti-RA33, results were comparable in early and established cases. Anti-RA33 values were correlated to disease activity (clinical and laboratory), to laboratory markers (urinary calcium, parathyroid hormone levels) and radiological evidence (LI) of bone resorption (r = 0.95, 0.63, 0.94, respectively). CONCLUSION: Anti-RA33 is detected in two-thirds of JIA patients and occurs with comparable frequency early in the disease. Its levels are correlated to disease activity and markers of bone resorption and it seems to convey diagnostic and prognostic insights for appropriate management.

Central and peripheral renin-angiotensin systems in ouabain-induced hypertension.

Chronic subcutaneous infusion of ouabain causes hypertension via central pathways involving angiotensin type 1 (AT(1)) receptor stimulation. The present study assessed plasma and tissue ANG I and II levels as well as AT1 receptor and angiotensin-converting enzyme (ACE) mRNA levels and binding densities by real-time PCR and in vitro autoradiography in relevant brain nuclei and peripheral tissues (heart and kidney) in rats at 1 and/or 2 wk after start of ouabain infusion at 50 microg/day. After 2 wk (but not after 1 wk), blood pressures significantly increased (+15 mmHg). At 2 wk, plasma ANG I and II levels were markedly suppressed by ouabain. In contrast, in the heart and kidneys, ANG I levels were not affected, and ANG II levels tended to decrease, whereas in the hypothalamus ANG II content clearly increased. At 1 wk, no changes in ACE and AT1 receptor densities were seen. After 2 wk, there were significant decreases in AT(1) receptor mRNA and densities in the organum vasculosum of the lamina terminalis (OVLT), subfornical organ (SFO), and paraventricular nucleus (PVN). ACE densities decreased only in the OVLT and SFO, but ACE mRNA showed more variable responses (decrease in OVLT vs. increase in PVN). In the kidneys, at 2 wk both AT1 receptor and ACE densities were decreased, but mRNA abundance did not change. The heart showed no significant changes. The increase in hypothalamic ANG II content and associated decreases in central AT1 receptor and ACE densities support the involvement of the brain renin-angiotensin system in the central hypertensive mechanism of action of ouabain.