[Expression and regulation of renal sodium-cotransporters and -antiporters, and related-transport proteins].

The authors' researches have been focused on pathogenic, physiological and biochemical mechanisms in hypertension and diabetes. Studies on hypertension were performed using salt-sensitive hypertensive Dahl rats as compared with the corresponding normotensive rats. Especially, implication with mobilization of electrolytes such as sodium, potassium, calcium and magnesium in hypertension gave rise to provocative to the author.

Activation of Na+-independent Mg2+ efflux by 20-hydroxyeicosatetraenoic acid in rat renal epithelial cells.

Renal epithelial cells may have Mg(2+) transport pathways that regulate intracellular free Mg(2+) concentration ([Mg(2+)](i)) and reabsorption into the body. In mag-fura 2 fluorescent measurement, extracellular Mg(2+) removal induced a Na(+)-independent [Mg(2+)](i) decrease. The [Mg(2+)](i) decrease was suppressed by methyl arachidonyl fluorophosphonate, a cytosolic and Ca(2+)-independent phospholipase A(2) (iPLA(2)) inhibitor, and bromoenol lactone, an iPLA(2) inhibitor, but it was not suppressed by a secretory phospholipase A(2) inhibitor.

Reorganization of ZO-1 by sodium-dependent glucose transporter activation after heat stress in LLC-PK1 cells.

Heat stress (HS) induces activation of high-affinity sodium-dependent glucose transporter (SGLT1) in porcine renal LLC-PK(1) cells. In this study, we investigated the roles of SGLT1 activation in reorganization of zonula occludens-1 (ZO-1), a cytosolic tight junction (TJ) protein, after HS. HS (42 degrees C, 3 h) caused decrease in transepithelial electrical resistance (TER).

Recovery from heat shock injury by activation of Na+-glucose cotransporter in renal epithelial cells.

Exposure of cells or organs to sublethal physical or chemical stresses induces disruption of cellular structures and functions. Here, we examined whether Na(+)-glucose cotransporter (SGLT1) is involved in the recovery from heat shock (HS) injury in porcine renal epithelial LLC-PK(1) cells. Recovery from HS (42 degrees C for 3 h, then 37 degrees C for 12 h) increased SGLT1 activity, assessed by [14C]alpha-methyl glucopyranoside uptake, and a maximal transport rate (V(max)) from 2.

Arachidonic acid-activated Na+-dependent Mg2+ efflux in rat renal epithelial cells.

Arachidonic acid (AA), a metabolite of membrane phospholipids, and its metabolites are increased in Mg2+ deficiency. We examined whether the extracellular Mg2+ concentration affects AA production and whether AA regulates a putative Na+-dependent Mg2+ efflux pathway in renal epithelial NRK-52E cells. We used the cells cultured in 5 mM Mg2+-containing medium for 2 days because they enable us to detect Na+-stimulated Mg2+ efflux that was not observed in normal culture medium.

Chicken DT40 cells stably transfected with the rat P2X7 receptor ion channel: a system suitable for the study of purine receptor-mediated cell death.

We have generated and characterised a clone of chicken DT40 lymphocytes stably transfected with the rat P2X(7) receptor (rP2X(7)). Successful transfection was confirmed by Western blotting. Under voltage clamp, P2X(7)-expressing cells responded to ATP and dibenzoyl-ATP (Bz-ATP) (a more potent P2X(7) receptor agonist) with a rapidly activating and sustained inward current.

Expression of GFP-tagged low affinity Na+-dependent glucose transporter in Xenopus oocytes and CHO cells.

A low-affinity and high-capacity Na(+)-dependent glucose transporter (SGLT2) was inserted into the expression vector tagging of green fluorescent protein (EGFP). The protein expression and glucose transport activity were examined in Xenopus oocytes and Chinese hamster ovary (CHO) cells. In Western blotting analysis, EGFP-tagged SGLT2 protein expressed in both Xenopus oocytes and CHO cells.

Up-regulation of Na+-dependent Mg2+ transport by nitric oxide and cyclic GMP pathway in renal epithelial cells.

A putative, Na(+)-dependent Mg(2+) transport pathway controls the intracellular free Mg(2+) concentration ([Mg(2+)](i)) in various mammalian cells. The characteristics of this Mg(2+) transport pathway have not been clarified. Herein, we examined the regulatory mechanism of Na(+)-dependent Mg(2+) efflux in renal epithelial NRK-52E cells.

[Fundamental and applied studies on transport and metabolism of electrolytes and glucose--aim to contact with molecular biology].

The authors' research focuses on polyuria, natriuresis, glucosuria, glycemia, and renal calcification in occupational lead poisoning and endemic fluorosis. Changes in electrolyte mobilization and in glucose metabolism and transport following the administration of lead compounds or fluoride were examined to elucidate these mechanisms. The results suggest fundamental approaches to the mechanism of aging and life style diseases.

Up-regulation of sodium-dependent glucose transporter by interaction with heat shock protein 70.

Heat shock stress induces some heat shock proteins, including Hsp70, and activates sodium-dependent glucose transport in porcine renal LLC-PK(1) cells, but its mechanisms have not been described in detail. We investigated whether sodium-dependent glucose transporter (SGLT1) interacts with Hsp70 to increase SGLT1 activity. Heat shock stress increased SGLT1 activity without changing SGLT1 expression.

Magnesium influx enhanced by nitric oxide in hypertensive rat proximal tubule cells.

An abnormal handling of renal magnesium has been suggested to cause salt-sensitive hypertension. The filtered magnesium is first reabsorbed in the proximal tubule. Amiloride has been shown to enhance renal magnesium conservation, but the regulatory mechanisms are unknown yet.

Phosphatidylinositol 3-kinase mediates inhibitory effect of angiotensin II on sodium/glucose cotransporter in renal epithelial cells.

Effects of angiotensin II (ANGII) on regulation of sodium/glucose cotransporter (SGLT1) activity were investigated in LLC-PK(1) cells, renal proximal epithelial cell line. ANGII inhibited alpha-[14C] methyl-D-glucopyranoside (AMG) uptake into LLC-PK(1) cells in a dose-dependent manner. This inhibition was based on a decrease in maximal transport rate (Vmax) of AMG from 2.

Estimation of endotoxin-like substances in deep seawater by using bioassay.

Deep seawater has recently been under trial as a fundamental material for mineral water, food, face lotion and an efficacious reagent for the cure of atopic dermatitis in Japan. However, little is known about the biologically effective substances, including toxic compounds in deep seawater. In this study, we investigated the effects of deep seawater on the function of murine macrophages in vitro, and examined the endotoxin-like substances in seawater.

Polyvalent cation-sensing mechanism increased Na(+)-independent Mg(2+) transport in renal epithelial cells.

Extracellular Ca(2+)/polyvalent cation-sensing receptor (CaSR) is capable of monitoring changes in extracellular polyvalent cation concentrations. In the present study, we investigated whether CaSR agonists reinforce the decrease of intracellular free Mg(2+) concentration ([Mg(2+)](i)) induced by extracellular Mg(2+) plus Na(+) removal. Interestingly, exposure of NRK-52E renal epithelial cells to increasing extracellular Mg(2+) concentrations from 0.

Differential regulation of Na(+),K(+)-ATPase and the Na(+)-coupled glucose transporter in hypertensive rat kidney.

Several Na(+) transporters are functionally abnormal in the hypertensive rat. Here, we examined the effects of a high-salt load on renal Na(+),K(+)-ATPase and the sodium-coupled glucose transporter (SGLT1) in Dahl salt-resistant (DR) and salt-sensitive (DS) rats. The protein levels of Na(+),K(+)-ATPase and SGLT1 in the DS rat were the same as those in the DR rat, and were not affected by the high-salt load.

Sodium fluoride increases intracellular calcium in rat renal epithelial cell line NRK-52E.

In our previous experiment using rats, fluoride was reported to cause renal calcification, whose mechanism was deduced to be due to an increase in parathyroid hormone (PTH) secretion. However fluoride-induced renal calcification that was independent of PTH has not been understood well in the nephron of fluoride-treated animals. Thus, we examined the effect of sodium fluoride on intracellular calcium mobilization in a normal rat kidney epithelial cell line (NRK-52E cells).

Role of glucocorticoid on interleukin-6-induced cellular functions in the mouse macrophage cell line (Mm 1).

To discover a role of glucocorticoid on interleukin-6 (IL-6)-induced responses of a macrophage, we investigated the effect of IL-6 and/or dexamethasone (Dex) on cellular functions of a mouse macrophage cell line (Mm1 cells). The results obtained were as follows. (1) Dex decreased the accumulation of tumor necrosis factor-alpha induced by IL-6, whereas nitric oxide production was enhanced by Dex.

Characterization of inhibition by chronic treatment with lithium ion on nerve growth factor-induced neuronal differentiation of rat PC12 pheochromocytoma cells.

To understand the mechanism underlying the neurotoxicity of lithium ion, we investigated the inhibition of the nerve growth factor-induced neuronal differentiation of rat PC12 pheochromocytoma cells induced by treatment with LiCl. Incubation with 0.1-3 mM LiCl from 30 min before nerve growth factor (NGF) treatment attenuated neurite outgrowth.

Lead inhibits nitric oxide production transiently by mRNA level in murine macrophage cell lines.

Lead inhibited the production of nitric oxide (NO) in cytokine-induced macrophage cell lines of RAW264 and Mm1. The decrease was revealed in the concentration of lead (0.1-10 micrograms/ml) which did not decrease the viability of these cells.

Changes in IgA and metals in serum and urine of human volume hypertension.

In this study, disturbance of immune response as a pathogenic mechanism for human volume hypertension was investigated and compared to nephritis in its correlation with the metals such as zinc, iron and aluminum as environmental factors. Urinary gamma-GTP excretions in patients with nephritis or hypertension were higher than in healthy people, whereas the plasma renin activity in these patients were lower on the average than in healthy individuals. Hypertensive patients participating in this study were diagnosed as the volume hypertension type from our clinical and other results.

A role of protein kinase C in the alteration of renal glucose-6-phosphatase activity caused by fluoride.

In this study, protein kinase C was demonstrated to operate as a down-regulator of glucose-6-phosphatase in the kidney, at least. Renal glucose-6-phosphatase activity reached a maximum level in 3 h after the administration of fluoride to rats. The incremental increase of renal glucose-6-phosphatase activity caused by fluoride administration was markedly amplified by the administration of staurosporine (66 micrograms/kg, i.

Effect of fluoride on the activities of the Na+/glucose cotransporter and Na+/K(+)-ATPase in brush border and basolateral membranes of rat kidney (in vitro and in vivo).

In this study, renal Na+/K(+)-ATPase activity was demonstrated to be strongly suppressed prior to the glucosuria caused by a fluoride dose (NaF 35 mg/kg, i.p.), and the 50% suppression of the enzyme activity was almost at the same dose of NaF, about 30 mg/kg, i.

Suppression of cytokine production in T helper type 2 cells by nitric oxide in comparison with T helper type 1 cells.

We examined the effect of nitric oxide (NO) on cytokine production in T helper (Th) cell subsets, using murine splenic CD4+ T cells and two types of Th clones. Interferon-gamma-treated murine peritoneal exudate cells (IFN-PEC) suppressed DNA synthesis to 60% of the control level in CD4+ T cells stimulated with the anti-CD3 monoclonal antibody. The production of IL-2 and IL-4 in the CD4+ T cells decreased to 63.

Inhibitory mechanisms of antibody production by nitrogen oxides released from activated macrophages during the immune response: relationship to energy consumption.

We investigated the relationship between the sensitivity of mouse splenocytes in immune response to nitrogen oxides and energy consumption rate of the cells. Macrophage-like cells (Mm1) pretreated with IL-6 served as the source of the nitrogen oxides. The antibody production of both 2,4,6-trinitrophenyl-keyhole limpet haemocyanin-primed splenocytes and B cell hybridomas was markedly reduced; about 20-40% of splenocytes and B cell hybridomas were killed by co-culture with IL-6-treated Mm1.