P2Y2 receptor activation inhibits the expression of the sodium-chloride cotransporter NCC in distal convoluted tubule cells.

Luminal nucleotide stimulation is known to reduce Na(+) transport in the distal nephron. Previous studies suggest that this mechanism may involve the thiazide-sensitive Na(+)-Cl(-) cotransporter (NCC), which plays an essential role in NaCl reabsorption in the cells lining the distal convoluted tubule (DCT). Here we show that stimulation of mouse DCT (mDCT) cells with ATP or UTP promoted Ca(2+) transients and decreased the expression of NCC at both mRNA and protein levels. Specific siRNA-mediated silencing of P2Y2 receptors almost completely abolished ATP/UTP-induced Ca(2+) transients and significantly reduced ATP/UTP-induced decrease of NCC expression. To test whether local variations in the intracellular Ca(2+) concentration ([Ca(2+)]i) may control NCC transcription, we overexpressed the Ca(2+)-binding protein parvalbumin selectively in the cytosol or in the nucleus of mDCT cells. The decrease in NCC mRNA upon nucleotide stimulation was abolished in cells overexpressing cytosolic PV but not in cells overexpressing either a nuclear-targeted PV or a mutated PV unable to bind Ca(2+). Using a firefly luciferase reporter gene strategy, we observed that the activity of NCC promoter region from -1 to -2,200 bp was not regulated by changes in [Ca(2+)]i. In contrast, high cytosolic calcium level induced instability of NCC mRNA. We conclude that in mDCT cells: (1) P2Y2 receptor is essential for the intracellular Ca(2+) signaling induced by ATP/UTP stimulation; (2) P2Y2-mediated increase of cytoplasmic Ca(2+) concentration down-regulates the expression of NCC; (3) the decrease of NCC expression occurs, at least in part, via destabilization of its mRNA.

Andersen's syndrome: a distinct periodic paralysis.

A previous study of 4 patients defined Andersen's syndrome (AS) as a triad of potassium-sensitive periodic paralysis, ventricular dysrhythmias, and dysmorphic features. AS appears to be distinct in terms of its genetic defect from the alpha-subunit of skeletal muscle sodium channel and the cardiac potassium channel responsible for most long QT syndromes (LQT1). We studied 11 additional patients with AS from 5 kindreds. Spontaneous attacks of paralysis were associated with hypokalemia, normokalemia, or hyperkalemia. All 11 patients had similar dysmorphic features. The QT interval was prolonged in all patients although only 4 were symptomatic. Genetic linkage studies excluded linkage to the alpha-subunit of the skeletal muscle sodium channel and to four distinct LQT loci. In addition, none of the common dihydropyridine receptor mutations responsible for hypokalemic periodic paralysis were present. We conclude that (1) AS is a genetically unique channelopathy affecting both cardiac and skeletal membrane excitability, (2) attacks of paralysis may be either hypokalemic or hyperkalemic, (3) a prolonged QT interval is an integral feature of this syndrome, and (4) a prolonged QT interval may be the only sign in an individual from an otherwise typical AS kindred. This may be confused with more common, potentially lethal LQT syndromes.

Race, gender, drug use, and participation in AIDS clinical trials. Lessons from a municipal hospital cohort.

OBJECTIVES: To determine whether participation rates of women, persons of color, and injection drug users in AIDS clinical trials are similar to those of other HIV/AIDS patients, and to examine whether differences in patients' knowledge of clinical trails or reasons for not participating explain differences in participation rates by gender, race, or drug use. DESIGN: Cross-sectional survey of patients with HIV disease. SETTING: Ambulatory practice of a municipal teaching hospital. PATIENTS: Two hundred sixty patients receiving primary care for HIV disease. MEASUREMENTS AND MAIN RESULTS: Overall, 22.3% of patients had participated in a clinical trail. Women, patients of color, and drug users were significantly less likely to have ever participated in an AIDS clinical trial (p < .05). Multiple logistic regression confirmed being a person of color (odds ratio [OR] 2.14; 95% confidence interval [CI] 1.12-4.08) and injection drug use (OR 2.09; 95% CI 1.08-4.04) as significant predictors of nonparticipation in AIDS clinical trials (p < .05). Patients of color and women reported less knowledge of clinical trials, and were less likely to have been told about clinical trials for which they were eligible (p < .05). Patients of color were half as likely as whites to cite ineligibility as their reason for not participating (10.4% vs 22.4%). and more likely to hold unfavorable opinions of clinical research (50.7% vs. 40.5%). Reasons for nonparticipation did not differ by gender. CONCLUSIONS: Even when AIDS clinical trials are available on-site, persons of color, women, and drug users are less likely to participate. Educational efforts for patients and providers are needed to remedy continuing disparities in participation by race, gender, and risk factor group in AIDS clinical trials.