scholarly journals A re-evaluation of the role of mitochondrial pyruvate transport in the hormonal control of rat liver mitochondrial pyruvate metabolism

1984 ◽  
Vol 223 (3) ◽  
pp. 677-685 ◽  
Author(s):  
A P Halestrap ◽  
A E Armston
Keyword(s):  
Respiratory Chain ◽  
Hormonal Regulation ◽  
Hormone Treatment ◽  
Liver Mitochondria ◽  
Hormonal Control ◽  
Protonmotive Force ◽  
Pyruvate Metabolism ◽  
Carboxylase Activity ◽  
Computer Simulation Studies

The inhibitor of mitochondrial pyruvate transport alpha-cyano-beta-(1-phenylindol-3-yl)-acrylate was used to inhibit progressively pyruvate carboxylation by liver mitochondria from control and glucagon-treated rats. The data showed that, contrary to our previous conclusions [Halestrap (1978) Biochem. J. 172, 389-398], pyruvate transport could not regulate metabolism under these conditions. This was confirmed by measuring the intramitochondrial pyruvate concentration, which almost equilibrated with the extramitochondrial pyruvate concentration in control mitochondria, but was significantly decreased in mitochondria from glucagon-treated rats, where rates of pyruvate metabolism were elevated. Computer-simulation studies explain how this is compatible with linear Dixon plots of the inhibition of pyruvate metabolism by alpha-cyano-4-hydroxycinnamate. Parallel measurements of the mitochondrial membrane potential by using [3H]triphenylmethylphosphonium ions showed that it was elevated by about 3 mV after pretreatment of rats with both glucagon and phenylephrine. There was no significant change in the transmembrane pH gradient. It is shown that the increase in pyruvate metabolism can be explained by a stimulation of the respiratory chain, producing an elevation in the protonmotive force and a consequent rise in the intramitochondrial ATP/ADP ratio, which in turn increases pyruvate carboxylase activity. Mild inhibition of the respiratory chain with Amytal reversed the effects of hormone treatment on mitochondrial pyruvate metabolism and ATP concentrations, but not on citrulline synthesis. The significance of these observations for the hormonal regulation of gluconeogenesis from L-lactate in vivo is discussed.

scholarly journals Stimulation of pyruvate transport in metabolizing mitochondria through changes in the transmembrane pH gradient induced by glucagon treatment of rats

1978 ◽  
Vol 172 (3) ◽  
pp. 389-398 ◽  
Author(s):  
A P Halestrap
Keyword(s):  
Membrane Potential ◽  
Respiratory Chain ◽  
Maximum Rate ◽  
Liver Mitochondria ◽  
Ph Gradient ◽  
O2 Uptake ◽  
Pyruvate Metabolism ◽  
The Matrix ◽  
Stimulation Of

Glucagon treatment of rats allowed the isolation of liver mitochondria with enhanced rates of pyruvate metabolism measured in either sucrose or KCl media. No change in the activity of the pyruvate carrier itself was apparent, but under metabolizing conditions, use of the inhibitor of pyruvate transport, alpha-cyano-4-hydroxycinnamate, demonstrated that pyruvate transport limited the rate of pyruvate metabolism. The maximum rate of transport under metabolizing conditions was enhanced by glucagon treatment. Problems involved in measuring the transmembrane pH gradient under metabolizing conditions are discussed and a variety of techniques are used to estimate the matrix pH. From the distribution of methylamine, ammonia and D-lactate and the Ki for inhibition by alpha-cyano-4-hydroxycinnamate it is concluded that the matrix is more acid than the medium and that the pH of the matrix rises after glucagon treatment. The increase in matrix pH stimulates pyruvate transport. The membrane potential, ATP concentration and O2 uptake were also increased under metabolizing conditions in glucagon-treated mitochondria. These changes were correlated with a stimulation of the respiratory chain which can be observed in uncoupled mitochondria [Yamazaki (1975) J. Biol. Chem. 250, 7924–7930]. The mitochondrial Mg2+ content (mean +/- S.E.M.) was increased from 38.8 +/- 1.2 (n = 26) to 47.5 +/- 2.0 (n = 26) ng-atoms/mg by glucagon and the K+ content from 126.7 +/- 10.3 (n = 19) ng-atoms/mg. This may represent a change in membrane potential induced by glucagon in vivo. The physiological significance of these results in the control of gluconeogenesis is discussed.

scholarly journals The rapid alteration by tri-iodo-l-thyronine in vivo of both the ADP/O ratio and the apparent H+/O ratio in hypothyroid-rat liver mitochondria

1987 ◽  
Vol 241 (3) ◽  
pp. 657-661 ◽  
Author(s):  
A Crespo-Armas ◽  
J Mowbray
Keyword(s):  
Liver Mitochondria ◽  
Proton Exchange ◽  
Bulk Phase ◽  
Rat Liver Mitochondria ◽  
Kinetic Properties ◽  
Protonmotive Force ◽  
Proton Pumps ◽  
Pulse Technique ◽  
Physiological Dose

Mitochondria from the livers of thyroidectomized rats have a lowered ADP/O ratio, which can be restored to normal within 15 min after intravenous injection of a near-physiological dose of tri-iodothyronine. Thyroidectomy lowered the measured delta pH, which appears to be compensated by a rise (not statistically significant) in the membrane potential, so that the protonmotive force is unaltered. A simple simulation technique is described for use in estimating H+/O ratios by the oxygen-pulse technique, which circumvents the problem that this ratio can be seriously underestimated because of re-uptake of protons from the bulk phase by the mitochondria before their expulsion is complete. By this procedure the H+/O ratio of hypothyroid mitochondria is shown to be lowered by the same factor as the ADP/O ratio, and both these ratios are very rapidly restored in parallel by hormone administration. Although these findings could be consistent with a proposal that tri-iodothyronine rapidly modulates by some mechanism the efficiency of the respiratory-chain-linked proton pumps, the kinetic properties of the proton exchange suggest that the bulk-phase protons measured may not reflect faithfully those that drive the ATP synthetase.

Nutritional and hormonal regulation of pyruvate metabolism in the liver.

1979 ◽  
Vol 236 (5) ◽  
pp. E501
Author(s):  
H G McDaniel
Keyword(s):  
Fatty Acids ◽  
Rat Liver ◽  
Hormonal Regulation ◽  
Co2 Fixation ◽  
Fasting Glucose ◽  
Insulin Injection ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Pyruvate Metabolism ◽  
Fasted Rats

The effect of fasting, glucose, and glucagon injection on pyruvate metabolism of rat liver mitochondria was studied. Fasting for 24 h caused a) a twofold increase in mitochondrial pyruvate uptake, b) fivefold increase in CO2 fixation, and c) no change in pyruvate decarboxylation. Injection of glucose to fasted rats 2 h prior to preparation suppressed by one-half the increase in mitochondrial pyruvate uptake and CO2 fixation and increased hepatic pyruvate content. Injection of glucagon together with glucose abolished the depression of pyruvate uptake by glucose but did not prevent the decrease in mitochondrial CO2 fixation or hepatic ketone content caused by glucose alone. The effects of insulin injection resembled that of glucose in decreasing hepatic ketone content, but differed by increasing pyruvate uptake without much change in CO2 fixation. It is concluded that the increase in gluconeogenesis induced by fasting is due to an increase in pyruvate uptake and carboxylation by hepatic mitochondria. The latter is due to the increased mobilization and oxidation of fatty acids induced by reciprocal changes in insulin and glucagon.

scholarly journals The influence of thyroxine administered in vivo on the transmembrane protonic electrochemical potential difference in rat liver mitochondria

1979 ◽  
Vol 178 (2) ◽  
pp. 505-507 ◽  
Author(s):  
S B Shears ◽  
J R Bronk
Keyword(s):  
Respiration Rate ◽  
Rat Liver ◽  
Hormone Treatment ◽  
Liver Mitochondria ◽  
Electrochemical Potential ◽  
Potential Difference ◽  
Rat Liver Mitochondria

When mitochondria from normal and thyroxine-treated rats were energized by incubation with succinate, phosphate and MgCl2, it was found that the hormone treatment increased the transmembrane protonic electrochemical potential difference by 16mV and the respiration rate by 46%. Other experiments show these changes to be associated with increases in the intramitochondrial K+ and phosphate concentrations.

148. HORMONAL REGULATION OF miRNA IN THE TESTIS

2009 ◽  
Vol 21 (9) ◽  
pp. 66 ◽  
Author(s):  
P. K. Nicholls ◽  
C. A. Harrison ◽  
L. O'Donnell ◽  
P. G. Stanton
Keyword(s):  
Protein Expression ◽  
Sertoli Cells ◽  
Hormonal Regulation ◽  
Molecular Mechanisms ◽  
Reproductive Hormones ◽  
Hormonal Control ◽  
In Vivo Model ◽  
Micro Rnas

Acute suppression of circulating reproductive hormones (FSH and testosterone) inhibits sperm release (spermiation) (1), although the molecular mechanisms of spermiation failure are poorly understood. Micro-RNAs (miRNAs) are small non-coding RNAs that regulate protein expression, and are essential for normal spermatogenesis. Recent studies suggest that miRNAs are exquisitely sensitive to hormonal control by FSH, LH and testosterone (2–4). This suggests that hormonal regulation of miRNAs in the testis following acute hormonal suppression may contribute to spermiation failure. Therefore, we hypothesised that gonadotrophin regulated miRNAs control spermiation outcome. We used array analysis to show that miRNA expression is hormonally regulated by FSH and testosterone in our rat in vivo model of spermiation failure and also in primary rat Sertoli cells by. qPCR validation revealed that miR-7b, -23a, -30c, -125b, -148b, -197, -483, -592, and -690 are all hormonally sensitive testicular miRNAs. Bioinformatic analyses of potential gene targets of these miRNAs predicted numerous protein components localised in the testicular tubulobulbar complex (TBC). The TBC is a podosome-like structure found between Sertoli cells and adjacent germ cells in the testis, and is thought to internalise intact inter-cellular structures and regulate spermatid head shape prior to spermiation. WASP, a TBC protein that regulates actin filament dynamics, contained a conserved binding site for miR-690 within its 3'UTR. Increased miR-690 expression following hormone suppression corresponded to a decrease in WASP protein expression in vivo and in vitro. In addition, transfection of miR-690 into HEK293T cells down-regulated WASP protein. Our results suggest that following hormone suppression, miR-690 is stimulated in the Sertoli cell, thereby inhibiting WASP protein expression. We conclude that miRNA-mediated disruption of TBC integrity potentially regulates spermatid disengagement. This study describes new molecular mechanisms in the testis that may control spermiation outcome of potential significance in male hormonal contraception.

scholarly journals Maturation in liver mitochondria of Ruthenium Red-sensitive calcium-ion-transport activity and the influence of glucagon administration in vivo and in utero

1981 ◽  
Vol 196 (1) ◽  
pp. 207-216
Author(s):  
Veronica Prpić ◽  
Fyfe L. Bygrave
Keyword(s):  
Rat Liver ◽  
Post Partum ◽  
Liver Mitochondria ◽  
In Utero ◽  
Ruthenium Red ◽  
Protonmotive Force ◽  
Period 2 ◽  
Calcium Ion Transport ◽  
Energy Dependent

The maturation of Ca2+ transport in mitochondria isolated from rat liver was examined, from 5 days before birth. The mitochondria used were isolated from liver homogenates by centrifugation at 22000g-min. Ca2+ transport by mitochondria isolated from foetal liver is energy-dependent and Ruthenium Red-sensitive. The transmembrane pH gradient in these mitochondria is higher by about 7mV and the membrane potential lower by about 20mV than in adult mitochondria. The inclusion of 2mm-Pi in the incubation medium enhances the protonmotive force by approx. 30mV. The rate of Ca2+ influx in foetal mitochondria measured in buffered KCl plus succinate is low until about 2–3h after birth, when it increases to about 60% of adult values; approx. 24h later it has reached near-adult values. Higher rates of Ca2+ influx are observed in the presence of 2mm-Pi; 3–5 days before birth the rates are about one-third of adult values and decline slightly as birth approaches. By 2–3h post partum they have reached adult values. The inclusion of 12.5μm-MgATP with the Pi stimulates further the initial rate of Ca2+ influx in foetal mitochondria. The rates observed are constant over the prenatal period examined and are 50–60% of those observed in adult mitochondria. Mitochondria isolated from foetal livers 4–5 days before birth retain the accumulated Ca2+ for about 50min in the presence of 2mm-Pi. In the period 2 days before birth to birth, this ability is largely lost, but by 2–3h after birth Ca2+ retention is similar to that of adult mitochondria. The presence of 12.5μm-MgATP progressively enhances the Ca2+ retention time as development proceeds until 2–3h after birth, when it becomes less sensitive to added MgATP. Glucagon administration to older foetuses in utero enhances both the rate of mitochondrial Ca2+ influx assayed in the presence of 2mm-Pi and the time for which mitochondria retain accumulated Ca2+ in the presence of 12.5μm-MgATP and 2mm-Pi. Its administration to neonatal animals leads to an increase in mitochondrial Ca2+ retention similar to that seen in adult mitochondria. The data provide evidence that the Ruthenium Red-sensitive Ca2+ transporter is potentially as active in foetal mitochondria 5 days before birth as it is in adult mitochondria. They also show that foetal mitochondria have an ability to retain accumulated Ca2+ reminiscent of mitochondria from tumour cells and from hormone-challenged rat liver.

scholarly journals Hormonal regulation of cholesterol 7alpha-hydroxylase specific activity, mRNA levels, and transcriptional activity in vivo in the rat

1997 ◽  
Vol 38 (12) ◽  
pp. 2483-2491 ◽  
Author(s):  
W M Pandak ◽  
D M Heuman ◽  
K Redford ◽  
R T Stravitz ◽  
J Y Chiang ◽  
...  
Keyword(s):  
Hormonal Regulation ◽  
Transcriptional Activity ◽  
Specific Activity ◽  
Mrna Levels

scholarly journals Protein Kinase A/CREB Signaling Prevents Adriamycin-Induced Podocyte Apoptosis via Upregulation of Mitochondrial Respiratory Chain Complexes

2017 ◽  
Vol 38 (1) ◽  
Author(s):  
Kewei Xie ◽  
Mingli Zhu ◽  
Peng Xiang ◽  
Xiaohuan Chen ◽  
Ayijiaken Kasimumali ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Protein Kinase A ◽  
Respiratory Chain ◽  
Mitochondrial Respiratory Chain ◽  
Peroxisome Proliferator ◽  
Respiratory Chain Complexes ◽  
Peroxisome Proliferator Activated Receptor ◽  
Kinase A ◽  
Mitochondrial Respiratory

ABSTRACT Previous work showed that the activation of protein kinase A (PKA) signaling promoted mitochondrial fusion and prevented podocyte apoptosis. The cAMP response element binding protein (CREB) is the main downstream transcription factor of PKA signaling. Here we show that the PKA agonist 8-(4-chlorophenylthio)adenosine 3′,5′-cyclic monophosphate–cyclic AMP (pCPT-cAMP) prevented the production of adriamycin (ADR)-induced reactive oxygen species and apoptosis in podocytes, which were inhibited by CREB RNA interference (RNAi). The activation of PKA enhanced mitochondrial function and prevented the ADR-induced decrease of mitochondrial respiratory chain complex I subunits, NADH-ubiquinone oxidoreductase complex (ND) 1/3/4 genes, and protein expression. Inhibition of CREB expression alleviated pCPT-cAMP-induced ND3, but not the recovery of ND1/4 protein, in ADR-treated podocytes. In addition, CREB RNAi blocked the pCPT-cAMP-induced increase in ATP and the expression of peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC1-α). The chromatin immunoprecipitation assay showed enrichment of CREB on PGC1-α and ND3 promoters, suggesting that these promoters are CREB targets. In vivo, both an endogenous cAMP activator (isoproterenol) and pCPT-cAMP decreased the albumin/creatinine ratio in mice with ADR nephropathy, reduced glomerular oxidative stress, and retained Wilm's tumor suppressor gene 1 (WT-1)-positive cells in glomeruli. We conclude that the upregulation of mitochondrial respiratory chain proteins played a partial role in the protection of PKA/CREB signaling.

Effect of Dietary Theophylline on Pyruvate Metabolism and Respiratory Activities in Liver Mitochondria

1972 ◽  
Vol 140 (4) ◽  
pp. 1472-1476 ◽  
Author(s):  
B. Friend ◽  
M. A. Mehlman ◽  
V. Devore ◽  
R. B. Tobin
Keyword(s):  
Liver Mitochondria ◽  
Pyruvate Metabolism
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