Proximal tubule dysfunction in cystine-loaded tubules: effect of phosphate and metabolic substrates

1996 ◽  
Vol 271 (3) ◽  
pp. F717-F722
Author(s):  
G. Bajaj ◽  
M. Baum
Keyword(s):  
Oxygen Consumption ◽  
Proximal Tubule ◽  
Tricarboxylic Acid Cycle ◽  
Dimethyl Ester ◽  
Proximal Tubules ◽  
Intracellular Atp ◽  
Metabolic Substrates ◽  
Rate Of Oxygen Consumption ◽  
Intracellular Phosphate

Intracellular cystine loading by use of cystine dimethyl ester (CDME) results in a generalized inhibition in proximal tubule transport due, in part, to a decrease in intracellular ATP. The present study examined the importance of phosphate and metabolic substrates in the proximal tubule dysfunction produced by cystine loading. Proximal tubule intracellular phosphorus was 1.8 +/- 0.1 in control tubules and 1.1 +/- 0.1 nmol/mg protein in proximal tubules incubated in vitro with CDME P < 0.001). Infusion of sodium phosphate in rabbits and subsequent incubation of proximal tubules with a high-phosphate medium attenuated the decrease in proximal tubule respiration and prevented the decrease in intracellular ATP with cystine loading. Tricarboxylic acid cycle intermediates have been shown to preserve oxidative metabolism in phosphate-depleted proximal tubules. In proximal tubules incubated with either 1 mM valerate or butyrate, there was a 42 and 34% reduction (both P < 0.05) in the rate of oxygen consumption with cystine loading. However, tubules incubated with 1 mM succinate or citrate had only a 13 and 14% P = NS) reduction in the rate of oxygen consumption, respectively. These data are consistent with a limitation of intracellular phosphate in the pathogenesis of the proximal tubule dysfunction with cystine loading.

scholarly journals Metabolic substrates alter attachment and differentiated functions of proximal tubule cell culture.

1994 ◽  
Vol 4 (11) ◽  
pp. 1908-1911
Author(s):  
M J Tang ◽  
R L Tannen
Keyword(s):  
Proximal Tubule ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Culture Media ◽  
Proximal Tubules ◽  
Proximal Tubule Cell ◽  
Metabolic Substrates ◽  
Standard Culture ◽  
Leucine Amino Peptidase ◽  
Proximal Tubular

Proximal tubules cultured in vitro gradually lose their differentiated functions. Because standard culture media lacks several substrates important for renal proximal tubule oxidative metabolism, whether a mixture of substrates including butyrate, alanine, and lactate (BAL) would modify growth and/or differentiated function of proximal tubular cells in culture was examined. Tubules cultured in media supplemented with 2 mM butyrate, alanine, and lactate exhibited enhanced attachment but did not exhibit an altered growth rate. Higher levels of phosphoenolpyruvate carboxykinase and leucine-amino peptidase were sustained, although these activities were still diminished in comparison with that in fresh tubules. Sodium-dependent glucose uptake and dome formation--other reflections of epithelial cell differentiated function--also were enhanced. These studies demonstrate that the substrates used to culture proximal tubules can modify both their attachment and their manifestation of differentiated function in culture.

Identification of an apical \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{Cl}^{-}{/}\mathrm{HCO}_{3}^{-}\) \end{document} exchanger in rat kidney proximal tubule

2003 ◽  
Vol 285 (3) ◽  
pp. C608-C617 ◽  
Author(s):  
Snezana Petrovic ◽  
Liyun Ma ◽  
Zhaohui Wang ◽  
Manoocher Soleimani
Keyword(s):  
Proximal Tubule ◽  
Apical Membrane ◽  
Rat Kidney ◽  
Proximal Tubules ◽  
Immunocytochemical Staining ◽  
Kidney Cortex ◽  
Rat Kidney Cortex ◽  
Kidney Proximal Tubule ◽  
Anion Transporter

SLC26A6 (or putative anion transporter 1, PAT1) is located on the apical membrane of mouse kidney proximal tubule and mediates [Formula: see text] exchange in in vitro expression systems. We hypothesized that PAT1 along with a [Formula: see text] exchange is present in apical membranes of rat kidney proximal tubules. Northern hybridizations indicated the exclusive expression of SLC26A6 (PAT1 or CFEX) in rat kidney cortex, and immunocytochemical staining localized SLC26A6 on the apical membrane of proximal tubules, with complete prevention of the labeling with the preadsorbed serum. To examine the functional presence of apical [Formula: see text] exchanger, proximal tubules were isolated, microperfused, loaded with the pH-sensitive dye BCPCF-AM, and examined by digital ratiometric imaging. The pH of the perfusate and bath was kept at 7.4. Buffering capacity was measured, and transport rates were calculated as equivalent base flux. The results showed that in the presence of basolateral DIDS (to inhibit [Formula: see text] cotransporter 1) and apical EIPA (to inhibit Na+/H+ exchanger 3), the magnitude of cell acidification in response to addition of luminal Cl– was ∼5.0-fold higher in the presence than in the absence of [Formula: see text]. The Cl–-dependent base transport was inhibited by ∼61% in the presence of 0.5 mM luminal DIDS. The presence of physiological concentrations of oxalate in the lumen (200 μM) did not affect the [Formula: see text] exchange activity. These results are consistent with the presence of SLC26A6 (PAT1) and [Formula: see text] exchanger activity in the apical membrane of rat kidney proximal tubule. We propose that SLC26A6 is likely responsible for the apical [Formula: see text] (and Cl–/OH–) exchanger activities in kidney proximal tubule.

Stimulation of phosphate transport in the proximal tubule by metabolic substrates

1984 ◽  
Vol 247 (4) ◽  
pp. F582-F587 ◽  
Author(s):  
S. R. Gullans ◽  
P. C. Brazy ◽  
L. J. Mandel ◽  
V. W. Dennis
Keyword(s):  
Proximal Tubule ◽  
Fluid Transport ◽  
Initial Rate ◽  
Tricarboxylic Acid Cycle ◽  
Phosphate Transport ◽  
Glucose Absorption ◽  
Metabolic Substrates ◽  
Tricarboxylic Acid Cycle Intermediates ◽  
Stimulation Of

Studies of phosphate transport in the proximal tubule have recently focused on interactions with cellular metabolism. The present studies demonstrate that two fatty acids, valerate and butyrate, and two tricarboxylic acid cycle intermediates, succinate and malate, stimulate net phosphate transport in the rabbit proximal tubule by 34-117%. Valerate had no effect on the total uptake of inorganic [32P]phosphate into suspensions of proximal tubules but did enhance the initial rate of influx. Net fluid transport was unaffected by these substrates although glucose absorption increased by 10-15% following the addition of either valerate or succinate. Since valerate, butyrate, and succinate are known to stimulate gluconeogenesis and respiration, we evaluated the role of gluconeogenesis in the stimulation of phosphate transport. The addition of 3-mercaptopicolinate (1 mM), an inhibitor of gluconeogenesis, did not alter phosphate transport, nor did it prevent the valerate-induced stimulation of phosphate transport. We conclude that valerate, butyrate, succinate, and malate enhance phosphate transport by the proximal convoluted tubule. This action appears to be unrelated to effects on gluconeogenesis and may be related to close links between phosphate transport and oxidative metabolism.

Calcium transport across the pars recta of cortical segment 2 proximal tubules

1986 ◽  
Vol 251 (4) ◽  
pp. F718-F724
Author(s):  
J. E. Bourdeau
Keyword(s):  
Proximal Tubule ◽  
Driving Forces ◽  
Proximal Tubules ◽  
Ion Diffusion ◽  
Low Concentrations ◽  
Pars Recta ◽  
Transepithelial Voltage ◽  
Lower Temperature ◽  
Tubule Fluid

Partes rectae of cortical segment 2 proximal tubules were dissected from rabbit kidneys and perfused in vitro. Ca concentrations of perfused and collected fluids were measured by continuous-flow microcolorimetry. Epithelial Ca permeability (P) was estimated from the bath-to-lumen movement of 45Ca. The transepithelial voltage (psi) and [Ca2+] difference were varied simultaneously by changing perfusate composition. Tubules that were perfused and bathed with an identical artificial ultrafiltrate of plasma displayed a lumen-negative psi, a collectate [Ca] greater than perfusate, and net Ca secretion. Tubules perfused with "late" proximal tubule fluid (high [Cl], low [HCO3], low concentrations of Na+-cotransported solutes) demonstrated a lumen-positive psi, a perfusate [Ca2+] greater than the bath, a collectate [Ca] less than perfusate, and net Ca absorption. Under each of these conditions, net Ca flux was in the direction predicted by the experimentally measured driving forces for diffusional Ca transport. Tubules that were cooled while being perfused with late proximal tubule fluid showed an increased lumen-positive psi but reduced net Ca absorption. The latter finding was consistent with reduced Ca ion diffusion related to a smaller P at the lower temperature. I conclude that Ca2+ diffusion is an important component of net Ca absorption in this segment of the nephron.

Oxygenation of frog gastric mucosa in vitro

1975 ◽  
Vol 229 (6) ◽  
pp. 1510-1513 ◽  
Author(s):  
GW Kidder ◽  
CW Montgomery
Keyword(s):  
Oxygen Consumption ◽  
Gastric Mucosa ◽  
Acid Secretion ◽  
Normal Pressure ◽  
Bathing Solution ◽  
Hyperbaric Chamber ◽  
Secretory Rate ◽  
Co2 Diffusion ◽  
Rate Of Oxygen Consumption

We have recently shown that 5% CO2/95% O2 in the serosal bathing solution, with 100% O2 in the mucosal solution, results in CO2-diffusion limitation of acid secretion in bullfrog gastric mucosa. Changing to 10% CO2/90% 02 on both surfaces doubles the acid secretory rate. We calculate that, were the rate of oxygen consumption to increase significantly as a result of secretory stimulation, the tissue would now be oxygen limited. This prediction is tested by raising the P02 by increasing the total pressure in a hyperbaric chamber. Since no change in acid secretory rate or potential difference was observed upon changing from PO2 = 0.9 to PO2 = 1.9 atm, we conclude that the tissue is not O2 limited at normal pressure. Decreasing PO2 below 0.9 atm, by contrast, decreases the acid secretory rate and raises both PD and resistance. We infer that the rate of oxygen consumption did not rise significantly when acid secretion was increased by supplying sufficient CO2.

EFFECT OF TEMPERATURE ON METABOLIC RATES OF LIVER AND BROWN FAT HOMOGENATES

1967 ◽  
Vol 45 (11) ◽  
pp. 1763-1771 ◽  
Author(s):  
Jane C. Roberts ◽  
Robert E. Smith
Keyword(s):  
Adipose Tissue ◽  
Oxygen Consumption ◽  
Brown Adipose Tissue ◽  
Brown Fat ◽  
Effect Of Temperature ◽  
Metabolic Rates ◽  
Brown Adipose ◽  
Rate Of Oxygen Consumption ◽  
Effects Of Temperature

The effects of temperature in vitro upon metabolic rates of homogenates of brown fat and liver from control and cold-acclimated rats have been examined over the range 10–37 °C. At all temperatures, brown adipose tissue exhibits a higher rate of oxygen consumption [Formula: see text] than does liver, α-ketoglutarate being used as substrate. At 10 °C, brown adipose tissue retains a larger percentage (36–38%) of its 37 °C metabolic rate than does liver (22–24%).Q10 values and energies of activation (Ea) have been determined and compared with other data reported for these tissues. At 20 °C, breaks appear in the Arrhenius plots for liver from both control and cold-acclimated rats and also for brown fat from control rats, but not for the brown fat from cold-acclimated rats. Thus brown adipose tissue from cold-acclimated rats retains relatively higher levels of respiration at temperatures below the 20 °C breaking point than does brown fat from control rats.In view of previously reported cold-induced increases in mass, vascularity, and [Formula: see text] of brown fat, this decreased temperature sensitivity in the cold-acclimated rats appears wholly consonant with the adaptive behavior of brown fat in its role as a thermogenic effector.

Abstract 406: Oxidative Stress Mediated Myocardial Lipid Dysfunction

2016 ◽  
Vol 119 (suppl_1) ◽  
Author(s):  
Manikandan Panchatcharam ◽  
Mini Chandra ◽  
Jonathan Fox ◽  
Shenuarin Bhuiyan ◽  
Wayne Orr ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Oxygen Consumption ◽  
Oxidative Phosphorylation ◽  
Ischemia Reperfusion ◽  
Cardiac Injury ◽  
Negative Regulator ◽  
Membrane Pore ◽  
Mitochondrial Superoxide ◽  
Rate Of Oxygen Consumption

Lipid phosphate phosphatases-3 control the conversion of bioactive lipid phosphates to their dephosphorylated counterparts. Oxidative stress transactivates microRNA-92a, which is a negative regulator of LPP3. We found that LPP3 expression was markedly downregulated in ischemic regions after ischemia/reperfusion (I/R) injury. We observed a similar trend in the myocardium from patients samples with acute MI at 24h. Our in vitro studies indicate that overexpression of LPP3 protects the cardiomyocyte against reactive oxygen species (ROS)-induced cardiac injury and knockout of LPP3 gene in the myocardium increases cardiac dysfunction and mortality. Using XF24 Seahorse analyzer we determined the effect of ROS on respiration in pluripotent stem cell-derived cardiomyocytes (iPSC-CM). Adding Phorbol 12-myristate 13-acetate (PMA) to these cells immediately increased oxygen consumption as compared to LPP3 overexpressed cells. This apparent increase in respiration was reversible by oligomycin, which blocks ATP synthase. The rate of oxygen consumption per cell was significantly lower in stimulated compared to LPP3 overexpressed iPSC-CM. The most noticeable difference in the O 2 consumption was found in the presence of carbonilcyanide p-trifluromethoxyphenylhydrazone (FCCP). FCCP is an inner membrane pore opener which resets the proton gradient between mitochondrial matrix and interspace, resulting in continuous transport of protons and consuming O 2 at the maximum potential. Remarkably, while the FCCP treatment increased O 2 consumption in LPP3 overexpressed cells (P<0.05), the treatment showed no effect on the O 2 consumption in the PMA stimulated alone. The result indicated that the low basal oxidative phosphorylation activity in stimulated cells was due to unusually low oxidative phosphorylation potential. To explore the free radical regulation of LPP3 overexpressed cells, superoxide anion was measured using dihydroethidium, a fluorescent cholesterol analog. The levels of superoxide radicals in PMA treated cells were consistently and significantly higher than the levels in LPP3 overexpressed cells (P<0.05). In turn, the radicals can be removed by adding MitoTEMPO (a specific scavenger of mitochondrial superoxide).

Lactate absorption in Thamnophis proximal tubule: transport versus metabolism

1980 ◽  
Vol 238 (3) ◽  
pp. F218-F228 ◽  
Author(s):  
P. H. Brand ◽  
R. S. Stansbury
Keyword(s):  
Proximal Tubule ◽  
Lactate Concentration ◽  
Flux Ratio ◽  
Proximal Tubules ◽  
Chemical Gradient ◽  
Flow Rates ◽  
Net Flux ◽  
Unidirectional Fluxes ◽  
Absorptive Flux

Proximal tubules from the kidney of Thamnophis (garter snake) were perfused in vitro and unidirectional fluxes of lactate measured using L(+)-[U-14C]lactate, (lactate concentration, 1 mM). The lumen-to-bath (absorptive) flux (Jlb lact) significantly exceeded the bath-to-lumen flux (backflux) (Jbl lact) in each of 12 tubules (seven distal proximal and five proximal proximal). The flux ratio (Jlb lact/Jbl lact) was approximately 3.00. At flow rates of 13-16 nl/min and lactate concentration of 1 mM the net flux was about 1.60 pmol . min-1 . mm-1 in both proximal proximal and distal proximal segments. Both fluxes were decreased by perfusion at 5 degrees C. To determin e the contribution of metabolism of lactate to its absorption, Jlb lact was measured at 25 degrees C in 10 distal proximal tubules during perfusion with [14C]lactate, lactate concentration, 1 mM, and with [methoxy-3H]inulin. In these experiments, the amount of 14C found in the bath was 93% of the amount of 14C absorbed from the lumen. Chromatography showed that all of the 14C found in the bath was [14C]lactate. These data establish that in Thamnophis proximal tubule lactate absorption occurs against an electro chemical gradient by transport of the intact lactate molecule without significant metabolism.

Gluconeogenesis from glutamine and lactate in the isolated humanrenal proximal tubule: longitudinal heterogeneity and lack of response to adrenaline

2001 ◽  
Vol 360 (2) ◽  
pp. 371-377 ◽  
Author(s):  
Agnès CONJARD ◽  
Mireille MARTIN ◽  
Jérôme GUITTON ◽  
Gabriel BAVEREL ◽  
Bernard FERRIER
Keyword(s):  
Proximal Tubule ◽  
Human Kidney ◽  
Glucose Production ◽  
Proximal Tubules ◽  
Renal Gluconeogenesis ◽  
Adrenaline Infusion ◽  
Gluconeogenic Substrates ◽  
Stimulation Of

Recent studies in vivo have suggested that, in humans in the postabsorptive state, the kidneys contribute a significant fraction of systemic gluconeogenesis, and that the stimulation of renal gluconeogenesis may fully explain the increase in systemic gluconeogenesis during adrenaline infusion. Given the potential importance of human renal gluconeogenesis in various physiological and pathophysiological situations, we have conducted a study in vitro to further characterize this metabolic process and its regulation. For this, successive segments (S1, S2 and S3) of human proximal tubules were dissected and incubated with physiological concentrations of glutamine or lactate, two potential gluconeogenic substrates that are taken up by the human kidney in vivo, and glucose production was measured. The effects of adrenaline, noradrenaline and cAMP, a well established stimulator of gluconeogenesis in animal kidney tubules, were also studied in suspensions of human renal proximal tubules. The results indicate that the three successive segments have about the same capacity to synthesize glucose from glutamine; by contrast, the S2 and S3 segments synthesize more glucose from lactate than the S1 segment. In the S2 and S3 segments, lactate appears to be a better gluconeogenic precursor than glutamine. The addition of cAMP, but not of adrenaline or noradrenaline, led to the stimulation of gluconeogenesis from lactate and glutamine by human proximal tubules. These results indicate that, in the human kidney in vivo, lactate might be the main gluconeogenic precursor, and that the stimulation of renal gluconeogenesis observed in vivo upon adrenaline infusion may result from an indirect action on the renal proximal tubule.

Oxygen consumption by bovine granulosa cells with prediction of oxygen transport in preantral follicles

2013 ◽  
Vol 25 (8) ◽  
pp. 1158 ◽  
Author(s):  
Dongxing Li ◽  
Gabe P. Redding ◽  
John E. Bronlund
Keyword(s):  
Oxygen Consumption ◽  
Granulosa Cells ◽  
Oxygen Transport ◽  
Oxygen Consumption Rate ◽  
Consumption Rate ◽  
Model Parameters ◽  
Preantral Follicles ◽  
Rate Of Oxygen Consumption ◽  
Key Parameter

The rate of oxygen consumption by granulosa cells is a key parameter in mathematical models that describe oxygen transport across ovarian follicles. This work measured the oxygen consumption rate of bovine granulosa cells in vitro to be in the range 2.1–3.3 × 10–16 mol cell–1 s–1 (0.16–0.25 mol m–3 s–1). The implications of the rates for oxygen transport in large bovine preantral follicles were examined using a mathematical model. The results indicate that oocyte oxygenation becomes increasingly constrained as preantral follicles grow, reaching hypoxic levels near the point of antrum formation. Beyond a preantral follicle radius of 134 µm, oxygen cannot reach the oocyte surface at typical values of model parameters. Since reported sizes of large bovine preantral follicles range from 58 to 145 µm in radius, this suggests that oocyte oxygenation is possible in all but the largest preantral follicles, which are on the verge of antrum formation. In preantral bovine follicles, the oxygen consumption rate of granulosa cells and fluid voidage will be the key determinants of oxygen levels across the follicle.

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