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Peng Xu, John J Gildea, Chi Zhang, Prasad Konkalmatt, Santiago Cuevas, Dora Bigler Wang, Hanh T Tran, Pedro A Jose, and Robin A Felder

Introduction Hypertension develops when renal, neural, and hormonal mechanisms fail to enable the body to excrete the ingested sodium, and the sodium that accumulates in the body can no longer be sequestered (for example, in interstitium

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P C Hubbard and I W Henderson

Introduction

The role of dopamine as a neurotransmitter within the central nervous system is well established. Over the last decade, however, it has become apparent that dopamine plays a number of important regulatory roles outside the confines of the nervous system, most notably in the kidney. Intrarenal dopamine can modify renal haemodynamics, stimulate the release of renin and inhibit the tubular reabsorption of sodium. It is now clear that dopamine is produced extraneurally by the kidney and acts locally on specific dopamine receptors, thus it is acting as a paracrine, or even autocrine, agent at this level. This review assesses the role of intrarenal dopamine in the regulation of sodium excretion by the nephron, and attempts to place it in the context of the actions of other natriuretic and antinatriuretic mechanisms.

Salt intake and renal dopamine production

Increasing dietary salt increases urinary dopamine output in man (Ball et al. 1978,

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E. K. Asem and B. K. Tsang

ABSTRACT

The existence and importance of the Na+/H+ exchanger in intracellular pH (pHi) regulation in ovarian cells was studied in acid-loaded avian granulosa cells by monitoring the recovery of normal pHi using a trapped fluorescein derivative as an indicator. The resting pHi of freshly isolated granulosa cells from preovulatory follicles was 680 ± 0·08 when the extracellular pH (pHo) and sodium concentration (Nao +) were 7·3 and 144 mmol/l respectively. While exposure of granulosa cells to high pHo (pHo > 745) medium shifted the pHi upward with time, incubation of the cells in low pHo (pH < 6·80) buffer resulted in a significant decrease in pHi. In contrast, pHi remained constant when pHo was varied between the broad range of 6·8–7·4. When the cytoplasm was acidified by treatment with nigericin in choline+ buffer, both the magnitude and rate of recovery of normal pHi was suppressed significantly with decreasing pHo, but increased in high pHo medium. The recovery of pHi was dependent upon the concentration of extracellular sodium, in that the recovery rate and magnitude increased concomitantly with increases in Nao + concentrations, while the recovery was abolished when Nao + was completely replaced with choline+. In addition, the sodium ionophore monensin enhanced the recovery rate of normal pHi in a concentration-dependent manner. This action of monensin was observed only when sodium was present in the incubation medium, indicating that Nao + entry is important for the recovery of normal pHi. Monensin also evoked further cytoplasmic alkalinization in fully recovered cells, with a relative net effect dependent upon the level of Nao + present. The recovery of pHi by acid-loaded cells was attenuated in a concentration-dependent manner by the Na+/H+ exchange inhibitor amiloride. These results clearly demonstrate in granulosa cells the presence of a pHi-regulating system that requires extracellular Na+ and is sensitive to amiloride.

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M Tiedge and S Lenzen

ABSTRACT

RINm5F insulinoma cells show a defective physiological insulin secretory response to glucose stimulation. The short chain carbonic acid sodium butyrate induced a growth arrest during a 72-h tissue culture period. In contrast to control RINm5F cells, 2 mm glucose increased insulin secretion by more than 70% in these sodium butyrate-treated cells (1 mm) without any further increase of the secretory rate between 2 and 20 mm glucose. This effect of sodium butyrate on insulin secretion was assessed in comparison with its effect on gene expression of the GLUT1 and GLUT2 glucose transporter, hexokinase type I and type II, glucokinase and insulin. Sodium butyrate at a 1 mm concentration decreased GLUT1 gene expression by nearly 50%, but did not induce gene expression of the low-affinity GLUT2 glucose transporter above the detection limit. Furthermore, sodium butyrate increased glucokinase gene expression by more than 50% and hexokinase type II gene expression by more than 100%, while insulin gene expression was increased only by 24%. Hexokinase type II enzyme activity was increased by more than 100% without a concomitant significant change of the glucokinase enzyme activity. Sodium butyrate (2 mm) caused effects comparable with those of 1 mm sodium butyrate. Thus the improved insulin secretory responsiveness of RINm5F insulinoma cells after sodium butyrate treatment at low non-physiological millimolar glucose concentrations can be interpreted as a result of an increased hexokinase-mediated metabolic flux rate through the glycolytic chain.

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E Buommino, D Pasquali, AA Sinisi, A Bellastella, F Morelli, and S Metafora

Retinoic acid (RA) and sodium butyrate (NaB) are regulators of cell growth and differentiation. We studied their effect on normal (SVC1) or v-Ki-ras-transformed (Ki-SVC1) rat seminal vesicle (SV) epithelial cell lines. The treatment of these cells with 10(-((7( M RA did not produce significant changes in the morphological and biochemical parameters analyzed. When RA was used in combination with 2 mM NaB, the treatment induced substantial morphological changes, apoptosis-independent growth arrest, up-regulation of tissue transglutaminase (tTGase), and down-regulation of beta and gamma RA receptor (RAR) mRNA expression. The same cells did not express RAR alpha either before or after NaB/RA treatment. A similar treatment did not change the amount of mRNA coding for the protein SV-IV (a typical differentiation marker of the SV epithelium) in normal or ras-transformed cells nor the level of v-Ki-ras mRNA in Ki-SVC1 cells. These findings suggest that a defective RA/RARs signaling pathway is probably the biochemical condition that underlies the unresponsiveness to RA of our in vitro culture system, and indirectly points to the possibility that the NaB/RA-induced effects were brought about by a cooperation at the transcription level between the histone deacetylase inhibitory activity of NaB and the ability of RA/RAR to modulate the expression of various genes involved in the control of cell growth and differentiation.

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Ariadni Spyroglou, Jenny Manolopoulou, Sibylle Wagner, Martin Bidlingmaier, Martin Reincke, and Felix Beuschlein

±2 °C, (relative humidity 60±5%) and on a 12 h light:12 h darkness circle. The animals were fed with standard breeding chow (sodium 0.24%, potassium 0.91%; Ssniff R/M-H, Soest, Germany) ad libitum with free access to tap water. The experiments were

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Márcia Faria, Daniela Félix, Rita Domingues, Maria João Bugalho, Paulo Matos, and Ana Luísa Silva

the sodium-iodide symporter (NIS), an intrinsic plasma membrane protein found at the basolateral membrane of thyroid follicular cells. It belongs to the human solute carrier (SLC) family of transporters and uptakes iodide through the co-transport of

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Alice Guyon and Jean-Louis Nahon

in frequency of discharge of action potentials is mediated through a decrease of voltage-gated sodium current and delayed rectifier-potassium current (thus inducing a slowing of the repolarization of the action potential; Guyon et al. 2005 a ). At

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Cinzia Puppin, Nadia Passon, Jerome M Hershman, Sebastiano Filetti, Stefania Bulotta, Marilena Celano, Diego Russo, and Giuseppe Damante

Introduction The sodium–iodide symporter (NIS) is a transmembrane protein that mediates active iodide transport across the membrane of thyrocytes, a fundamental step in thyroid hormone synthesis and for adequate radioiodine concentration to detect

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Maria D'Agostino, Marialuisa Sponziello, Cinzia Puppin, Marilena Celano, Valentina Maggisano, Federica Baldan, Marco Biffoni, Stefania Bulotta, Cosimo Durante, Sebastiano Filetti, Giuseppe Damante, and Diego Russo

requires adequate tumor tissue expression of genes that play key roles in iodine metabolism, in particular those encoding the thyroid-stimulating hormone receptor (TSHR) and the sodium/iodide symporter (NIS) ( Schlumberger et al . 2007 , Wartofsky & Van