• The Korean Journal of Physiology and Pharmacology
• /
• v.6 no.5
• /
• pp.261-267
• /
• 2002

The aim of the present study was to investigate the interaction of $estradiol-17{\beta}-bovine$ serum albumin $(E_2-BSA)$ and calcitropic hormones, such as parathyroid hormone, calcitonin, and vitamin D, in regulation of $Ca^{2+}$ uptake in primary cultured renal proximal tubule cells. Statistically significant increase in $Ca^{2+}$ uptake was found from 2 hours after $(E_2-BSA)\;(10^{-9}\;M)$ treatment, while $estradiol-17{\beta}\;(10^{-9}\;M)$ did not affect. Treatment of the cells with $(E_2-BSA)\;(10^{-9}\;M)$ together with parathyroid hormone (PTH) $(10^{-8}\;M),$ vitamin D $(10^{-8}\;M),$ or calcitonin $(10^{-8}\;M)$ significantly stimulated $Ca^{2+}$ uptake by 32.50%, 29.30%, or 27.75%, respectively, compared with the control. However, calcitropic hormones did not exhibit any synergistic effect on the E2-BSA-induced stimulation. $E_2-BSA$ significantly increased cAMP generation and PKC activity. The stimulatory effect of cotreatment of $E_2-BSA$ and PTH or vitamin D was blocked by SQ22536 (an adenylate cyclase inhibitor) and staurosporine (a PKC inhibitor), but the effect of cotreatment of $E_2-BSA$ and calcitonin was not blocked. Furthermore, 8-Br-cAMP and TPA (an artificial PKC promoter) increased $Ca^{2+}$ uptake by 25.51% and 16.47%, respectively, compared with the control. In conclusion, $E_2-BSA$ combined with calcitropic hormones regulated $Ca^{2+}$ uptake partially via cAMP and PKC-dependent mechanisms in renal proximal tubule cells.

• Korean Journal of Veterinary Research
• /
• v.37 no.2
• /
• pp.311-319
• /
• 1997

The mechanisms of $estradiol-17{\beta}$ regulating growth of both normal and neoplastic cells are not clear until now. In studies using various estrogen-dependent breast cell lines, it is recently known that estrogen controls the cell growth by regulating the expression of growth factors and/or their receptors. In the present study, we investigated the effects of $estradiol-17{\beta}$on cell growth and IGF-I binding sites using primary cultured renal proximal tubule cells. We have obtained results as follows : $Estradiol-17{\beta}(10^{-9})$ has stimulatory effects in cell growth. Cotreatment of $estradiol-17{\beta}(10^{-9}M)$ and $IGF-I(5{\times}10^{-8}M)$ significantly increased the growth of primary rabbit renal proximal tubule cells compared to that of $estradiol-17{\beta}$ or IGF-I alone treated cells. In binding studies, we found that the binding of $^{125}IGF-I$ on cell membranes was incubation time- and temperature-dependent. Incubation at $37^{\circ}C$ results in higher binding of $^{125}IGF-I$ than that of $23^{\circ}C$ or $4^{\circ}C$. Maximum binding was observed at $37^{\circ}C$ between 30 and 60 minutes. The binding of $^{125}IGF-I$ to both control and $estradiol-17{\beta}-treated$ cells was inhibited by unlabelled $IGF-I(10^{-8}{\sim}10^{-12}M)$ in a concentration-dependent manner. However, EGF did not compete for $^{125}IGF-I$ binding at $10^{-8}{\sim}10^{-12}M$. IGF-I binding to the membranes from both control and $estradiol-17{\beta}-treated$ cells was also analyzed. We found that $estradiol-17{\beta}-treated$ cells exhibited higher binding activity for IGF-I. When $estradiol-17{\beta}$ or tamoxifen alone, or $estradiol-17{\beta}$ and tamoxifen cotreated cells were compared, the binding ratio of $^{125}I-IGF-I$ of $estradiol-17{\beta}-treated$ cell was significantly increased but was similar to control in both $estradiol-17{\beta}$ and tamoxifen cotreated cell. These results suggest that $estradiol-17{\beta}$ in part controls cell proliferation by regulating the expression of IGF-I receptors in primary rabbit renal proximal tubule cells.

• The Korean Journal of Physiology and Pharmacology
• /
• v.2 no.5
• /
• pp.601-609
• /
• 1998

The present study was undertaken to examine the role of phospholipase $A_2\;(PLA_2)$ in oxidant-induced inhibition of phosphate transport in primary cultured rabbit renal proximal tubule cells. Uptakes of phosphate and glucose were dose-dependently inhibited by an oxidant t-butylhydroperoxide (tBHP), and the significant inhibition appeared at 0.025 mM of tBHP, whereas tBHP-induced alterations in lipid peroxidation and cell viability were seen at 0.5 mM. tBHP stimulated arachidonic acid (AA) release in a dose-dependent fashion. A $PLA_2$ inhibitor mepacrine prevented tBHP-induced AA release, but it did not alter the inhibition of phosphate uptake and the decrease in cell viability induced by tBHP. tBHP-induced inhibition of phosphate transport was not affected by a PKC inhibitor, staurosporine. tBHP at 0.1 mM did not produce the inhibition of $Na^+-K^+-ATPase$ activity in microsomal fraction, although it significantly inhibited at 1.0 mM. These results suggest that tBHP can inhibit phosphate uptake through a mechanism independent of $PLA_2$ activation, irreversible cell injury, and lipid peroxidation in primary cultured rabbit renal proximal tubular cells.

• The Korean Journal of Physiology
• /
• v.27 no.2
• /
• pp.227-232
• /
• 1993

The temperature dependence of $Na^+-dependent$ succinate uptake was studied in brush border (BBMV) and basolateral (BLMV) membrane vesicles isolated from the rabbit kidney cortex. The succinate uptake was markedly altered by temperature in a similar fashion in both membranes. The temperature dependence was characterized by a nonlinear Arrhenius plot with a break point at 22 and $25^{\circ}C$ for BBMV and BLMV, respectively. The activation energy was 3.91 and 17.09 kcal/mole at above and below the break point respectively, far BBMV; 2.65 and 14.05 kcal/mole, respectively, for BLMV. When temperature increased f개m 20 to $35^{\circ}C$, the Vmax of succinate transport increased from $3.49{\pm}0.11\;to\;5.90{\pm}0.86\;nmole/mg/5\;sec$ for BBMV and from $2.86{\pm}0.25\;to\;3.63{\pm}0.32\;nmole/mg/5\;sec$ for BLMV, with no change in Km in both membranes. These results suggest that renal dicarboxylate transport is similarly sensitive to a change in membrane physical state in BBMV and BLMV.

• The Korean Journal of Physiology
• /
• v.25 no.2
• /
• pp.179-188
• /
• 1991

Effect of a sulfhydryl reagent, p-chloromercuribenzoic acid (PCMB), on the transport of succinate was studied in brush border (BBMV) and basolateral (BLMV) membrane vesicles isolated from rabbit renal cortex. PCMB induced an irreversible inhibition of the $Na^+-dependent$ succinate uptake in a dose-dependent manner with $IC_{50}$ of 55 and $65\;{\mu}M$ in BBMV and BLMV, respectively. The inhibitory effect of PCMB was prevented by a pretreatment of vesicles with dithiothreitol. PCMB did not increase $Na^+$ permeability at concentrations inhibiting succinate uptake. The PCMB inhibition of succinate uptake was due to a change in Vmax, but not in Km. When membrane vesicles were pretreated with PCMB in the presence of unlabelled succinate, the inhibitory effect was significantly reduced. In both BBMV and BLMV, succinate uptake was inhibited by various sulfhydryl reagents with the inhibitory potency of following order: $HgCl_2$>DTNB>PCMBS>PCMB. These results suggest that sulfhydryl groups are essential for dicarboxylate transport and that they may be located at or near substrate binding sites of the transporters in renal brush border and basolateral membranes.

• BMB Reports
• /
• v.57 no.2
• /
• pp.116-121
• /
• 2024

We investigated the therapeutic potential of bone marrow-derived mesenchymal stem cell-conditioned medium (BMSC-CM) on immortalized renal proximal tubule epithelial cells (RPTEC/TERT1) in a fibrotic environment. To replicate the increased stiffness characteristic of kidneys in chronic kidney disease, we utilized polyacrylamide gel platforms. A stiff matrix was shown to increase α-smooth muscle actin (α-SMA) levels, indicating fibrogenic activation in RPTEC/TERT1 cells. Interestingly, treatment with BMSC-CM resulted in significant reductions in the levels of fibrotic markers (α-SMA and vimentin) and increases in the levels of the epithelial marker E-cadherin and aquaporin 7, particularly under stiff conditions. Furthermore, BMSC-CM modified microRNA (miRNA) expression and reduced oxidative stress levels in these cells. Our findings suggest that BMSC-CM can modulate cellular morphology, miRNA expression, and oxidative stress in RPTEC/TERT1 cells, highlighting its therapeutic potential in fibrotic kidney disease.

• The Korean Journal of Physiology
• /
• v.30 no.2
• /
• pp.257-267
• /
• 1996

Diabetes mellitus is associated with a wide range of pathophysiologic changes in the kidney. This study was designed to examine the mechanisms by which glucose modulates the expression of polarized membrane transport functions in primary cultured rabbit renal proximal tubule cells. Results are as follows: The rate of 30 minute $Rb^{+}$ uptake was significantly higher($137.76{\pm}5.40%$) in primary renal tubular cell cultures treated with 20 mM glucose than that of 5 mM glucose. Not the level of mRNA for the ${\alpha}$ subunit of Na, K-ATPase but that of ${\beta}$ subunit was elevated in primary cultures treated with high glucose. The initial rate of methyl-${\alpha}$-D-glucopyranoside(${\alpha}$-MG) uptake was significantly lower($71.91{\pm}3.02%$) in monolayers treated with 20 mM glucose than that of 5 mM glucose. There was a tendency of an increase in phlorizin binding site in cells treated with 5 mM glucose. However, 3-O-methyl-D-glucose(3-O-MG) uptake was not affected by glucose concentration in culture media. TPA inhibited $Rb^{+}$ uptake by $63.61{\pm}1.94\;and\;45.80{\pm}1.36%$ and ${\alpha}$-MG uptake by $48.54{\pm}3.69\;and\;41.87{\pm}6.70%$ in the cells treated with 5 and 20 mM glucose, respectively. Also TPA inhibited mRNA expression of Na/glucose cotransporter in cells grown in 5mM glucose medium. cAMP significantly stimulated ${\alpha}$-MG uptake by $114.65{\pm}5.70%$ in cells treated with 5mM glucose, while it did not affect ${\alpha}$-MG uptake in cell treated with 20 mM glucose. However, cAMP inhibited $Rb^{+}$ uptake by $76.69{\pm}4.16\;and\;66.87{\pm}2.41%$ in cells treated with 5 and 20 mM glucose, respectively. In conclusion, the activity of the renal proximal tubular Na,K-ATPase is elevated in high glucose concentration. In contrast, the activity of the Na/glucose cotransport system is inhibited. High glucose may in part affect the activity of the Na,K-ATPase and the Na/glucose cotransport system by controlling the protein kinase C and/or A signal transduction pathway in primary cultured renal proximal tubule cells.

• Archives of Pharmacal Research
• /
• v.28 no.4
• /
• pp.421-432
• /
• 2005

In order to understand the renal reabsorption mechanism of neutral amino acids via amino acid transporters, we have isolated human L-type amino acid transporter 2 (hLAT2) and human T-type amino acid transporter 1 (hTAT1) in human, then, we have examined and compared the gene structures, the functional characterizations and the localization in human kidney. Northern blot analysis showed that hLAT2 mRNA was expressed at high levels in the heart, brain, placenta, kidney, spleen, prostate, testis, ovary, lymph node and the fetal liver. The hTAT1 mRNA was detected at high levels in the heart, placenta, liver, skeletal muscle, kidney, pancreas, spleen, thymus and prostate. Immunohistochemical analysis on the human kidney revealed that the hLAT2 and hTAT1 proteins coexist in the basolateral membrane of the renal proximal tubules. The hLAT2 transports all neutral amino acids and hTAT1 transports aromatic amino acids. The basolateral location of the hLAT2 and hTAT1 proteins in the renal proximal tubule as well as the amino acid transport activity of hLAT2 and hTAT1 suggests that these transporters contribute to the renal reabsorption of neutral and aromatic amino acids in the basolateral domain of epithelial proximal tubule cells, respectively. Therefore, LAT2 and TAT1 play essential roles in the reabsorption of neutral amino acids from the epithelial cells to the blood stream in the kidney. Because LAT2 and TAT1 are essential to the efficient absorption of neutral amino acids from the kidney, their defects might be involved in the pathogenesis of disorders caused by a disruption in amino acid absorption such as blue diaper syndrome.

• Microbiology and Biotechnology Letters
• /
• v.5 no.4
• /
• pp.185-189
• /
• 1977

After administering overdosage of vitamin A, D ＆ E to the matured female chicken, the changes of the epithelial cells of the proximal convoluted tubule were observed and the results were summarized at follows. In the group treated with 2.5 ml of Rovisol, the mitochondria were slightly swollen and free ribosomes were mildly increased. The mitochondria were more swollen, microvilli were somewhat irregular and fused chondriosphere were noted when the chicken were treated with 7.5 ml of Rovisol. When the thicken were treated with 12.5ml of Rovisol the cell sap was markedly edematous so that the cellular organelles seemed to reduce. Also noted were chondriospgere and increased free ribosomes. According to the results of this study it is considered that the changes of the epithelial cells of proximal convoluted tubules of tile matured hens after administering overdosage of vitamin complex are mainly cellular swelling and are reversible ones.

• Journal of Medicine and Life Science
• /
• v.15 no.2
• /
• pp.37-41
• /
• 2018

Mitochondrial injury in renal tubule has been recognized as a major contributor in acute kidney injury (AKI) pathogenesis. Ischemic insult, nephrotoxin, endotoxin and contrast medium destroy mitochondrial structure and function as well as their biogenesis and dynamics, especially in renal proximal tubule, to elicit ATP depletion. Mitochondrial fatty acid ${\beta}$-oxidation (FAO) is the preferred source of ATP in the kidney, and its impairment is a critical factor in AKI pathogenesis. This review explores current knowledge of mitochondrial dysfunction and energy depletion in AKI and prospective views on developing therapeutic strategies targeting mitochondrial dysfunction in AKI.