Sodium bicarbonate cotransporter NBCe2 gene variants increase sodium and bicarbonate transport in human renal proximal tubule cells.

Rationale: Salt sensitivity of blood pressure affects >30% of the hypertensive and >15% of the normotensive population. Variants of the electrogenic sodium bicarbonate cotransporter NBCe2 gene, SLC4A5, are associated with increased blood pressure in several ethnic groups. SLC4A5 variants are also highly associated with salt sensitivity, independent of hypertension.

The sodium-bicarbonate cotransporter NBCe2 (slc4a5) expressed in human renal proximal tubules shows increased apical expression under high-salt conditions.

The electrogenic sodium bicarbonate cotransporter (NBCe2) is encoded by SLC4A5, variants of which have been associated with salt sensitivity of blood pressure, which affects 25% of the adult population. NBCe2 is thought to mediate sodium bicarbonate cotransport primarily in the renal collecting duct, but NBCe2 mRNA is also found in the rodent renal proximal tubule (RPT). The protein expression or function of NBCe2 has not been demonstrated in the human RPT.

The cooperative roles of the dopamine receptors, D1R and D5R, on the regulation of renal sodium transport.

Determining the individual roles of the two dopamine D1-like receptors (D1R and D5R) on sodium transport in the human renal proximal tubule has been complicated by their structural and functional similarity. Here we used a novel D5R-selective antagonist (LE-PM436) and D1R- or D5R-specific gene silencing to determine second messenger coupling pathways and heterologous receptor interaction between the two receptors. D1R and D5R colocalize in renal proximal tubule cells and physically interact, as determined by co-immunoprecipitation and fluorescent resonance energy transfer microscopy.

A linear relationship between the ex-vivo sodium mediated expression of two sodium regulatory pathways as a surrogate marker of salt sensitivity of blood pressure in exfoliated human renal proximal tubule cells: the virtual renal biopsy.

Background: Salt sensitivity (SS) of blood pressure (BP) affects 25% of adults, shares comorbidity with hypertension, and has no convenient diagnostic test. We tested the hypothesis that urine-derived exfoliated renal proximal tubule cells (RPTCs) could diagnose the degree of an individual's SS of BP.

Methods: Subjects were selected who had their SS of BP determined 5 y prior to this study (salt-sensitive: ≥7 mm Hg increase in mean arterial pressure (MAP) following transition from a random weekly diet of low (10 mmol/day) to high (300 mmol/day) sodium (Na(+)) intake, N=4; inverse salt-sensitive (ISS): ≥7 mm Hg increase in MAP transitioning from a high to low Na(+) diet, N=3, and salt-resistant (SR): <7 mm Hg change in MAP transitioned on either diet, N=5).

Isolation, growth, and characterization of human renal epithelial cells using traditional and 3D methods.

The kidney is a highly heterogeneous organ that is responsible for fluid and electrolyte balance. Much interest is focused on determining the function of specific renal epithelial cells in humans, which can only be accomplished through the isolation and growth of nephron segment-specific epithelial cells. However, human renal epithelial cells are notoriously difficult to maintain in culture.

Salt sensitivity of blood pressure is associated with polymorphisms in the sodium-bicarbonate cotransporter.

Previous studies have demonstrated that single nucleotide polymorphisms (SNPs) of the sodium-bicarbonate co-transporter gene (SLC4A5) are associated with hypertension. We tested the hypothesis that SNPs in SLC4A5 are associated with salt sensitivity of blood pressure in 185 whites consuming an isocaloric constant diet with a randomized order of 7 days of low Na(+) (10 mmol/d) and 7 days of high Na(+) (300 mmol/d) intake. Salt sensitivity was defined as a ≥ 7-mm Hg increase in mean arterial pressure during a randomized transition between high and low Na(+) diet.

A comparison of the natriuretic and kaliuretic effects of cicletanine and hydrochlorothiazide in prehypertensive and hypertensive humans.

Objectives: The aim of this study was to compare the single-dose effects of thiazide-type diuretics cicletanine and hydrochlorothiazide (HCTZ), on natriuresis and kaliuresis in prehypertensive and treatment-naïve, stage 1 hypertensive patients and to explore the impact of GRK4 gene polymorphisms on thiazide-induced urinary electrolyte excretion.

Methods: The study was a randomized, double-blind, placebo-controlled, three-period, four-treatment, balanced incomplete block, cross-over study in male patients assigned to treatment sequences consisting of placebo, cicletanine 50 mg, cicletanine 150 mg, and HCTZ 25 mg, doses used to treat hypertension. Cumulative urine samples were collected predosing and over 24 h after dosing in each period to compare urine electrolyte excretion profiles of potassium (UKV), sodium (UNaV), magnesium, calcium, phosphate, chloride, and pH among groups.

HK-2 human renal proximal tubule cells as a model for G protein-coupled receptor kinase type 4-mediated dopamine 1 receptor uncoupling.

HK-2 human renal proximal tubule cells (RPTC) are commonly used in the in vitro study of "normal" RPTCs. We discovered recently that HK-2 cells are uncoupled from dopamine 1 receptor (D(1)R) adenylyl cyclase (AC) stimulation. We hypothesized that G protein-coupled receptor kinase type 4 (GRK4) single nucleotide polymorphisms may be responsible for the D(1)R/AC uncoupling in HK-2.

Intrarenal dopamine D1-like receptor stimulation induces natriuresis via an angiotensin type-2 receptor mechanism.

We explored the effects of direct renal interstitial stimulation of dopamine D(1)-like receptors with fenoldopam, a selective D(1)-like receptor agonist, on renal sodium excretion and angiotensin type-2 (AT(2)) receptor expression and cellular distribution in rats on a high-sodium intake. In contrast to vehicle-infused rats, sodium excretion increased in fenoldopam-infused rats during each of three 1-hour experimental periods (<0.001).

Renal interstitial guanosine cyclic 3', 5'-monophosphate mediates pressure-natriuresis via protein kinase G.

Pressure-natriuresis is the physiological protective mechanism whereby elevation of blood pressure induces a rapid increase in renal sodium (Na+) excretion. Pressure-natriuresis abnormalities are common to all forms of hypertension. We tested the hypothesis that pressure-natriuresis is mediated by renal interstitial (RI) cGMP and protein kinase G (PKG).

Constitutional sequence variation in the Fanconi anaemia group C (FANCC) gene in childhood acute myeloid leukaemia.

The extent to which genetic susceptibility contributes to the causation of childhood acute myeloid leukaemia (AML) is not known. The inherited bone marrow failure disorder Fanconi anaemia (FA) carries a substantially increased risk of AML, raising the possibility that constitutional variation in the FA (FANC) genes is involved in the aetiology of childhood AML. We have screened genomic DNA extracted from remission blood samples of 97 children with sporadic AML and 91 children with sporadic acute lymphoblastic leukaemia (ALL), together with 104 cord blood DNA samples from newborn children, for variations in the Fanconi anaemia group C (FANCC) gene.