scholarly journals Dual effect of spermine on mitochondrial Ca2+ transport

1992 ◽  
Vol 286 (2) ◽  
pp. 597-602 ◽  
Author(s):  
S Lenzen ◽  
W Münster ◽  
I Rustenbeck
Keyword(s):  
Uptake Rate ◽  
Initial Rate ◽  
Experimental Situation ◽  
Kinetic Characteristics ◽  
Dual Effect ◽  
Apparent Paradox ◽  
Resolution System ◽  
Initial Uptake Rate ◽  
Accumulation Capacity ◽  
Stimulation Of

1. A dual effect of the polyamine spermine on Ca2+ uptake by isolated rat liver, brain and heart mitochondria could be demonstrated by using a high-resolution system for studying mitochondrial Ca2+ transport. Depending on the experimental situation, spermine had an inhibiting or accelerating effects on mitochondrial Ca(2+)-uptake rate, but invariably increased the mitochondrial Ca2+ accumulation. 2. Both effects were concentration-dependent and clearly discernible on the basis of their different kinetic characteristics. For mitochondria from all three tissues the half-maximally effective concentration for inhibition of the initial rate of Ca2+ uptake was approx. 180 microM, whereas that for the subsequent stimulation of Ca2+ accumulation was approx. 50 microM. 3. Acceleration of the initial uptake rate could be seen when the mitochondria were preloaded with spermine during a 2 min preincubation period and thereafter incubated in a medium without spermine. 4. When such spermine-preloaded mitochondria were incubated in a spermine-containing medium, the increase in Ca(2+)-accumulation capacity was maintained in spite of an unchanged rate of Ca2+ uptake. 5. Mg2+ interacted with the effects of spermine in a differential manner, enhancing the initial inhibition of the rate of mitochondrial Ca2+ uptake and diminishing the subsequent stimulation of mitochondrial Ca2+ accumulation. 6. This dual effect of spermine on mitochondrial Ca2+ transport resolves the apparent paradox that a polycationic compound can act as a stimulator of Ca2+ uptake.

Effects of l-leucine, its 2-keto acid metabolite and its nonmetabolized analogue on rat tumoral islet cell function

1988 ◽  
Vol 1 (1) ◽  
pp. 69-76 ◽  
Author(s):  
V. Leclercq-Meyer ◽  
J. Marchand ◽  
A. Sener ◽  
F. Blachier ◽  
W. J. Malaisse
Keyword(s):  
Insulin Release ◽  
Cell Function ◽  
Islet Cells ◽  
Adenine Nucleotides ◽  
Secretory Response ◽  
Acid Metabolite ◽  
Dual Effect ◽  
Islet Cell Function ◽  
Insulinoma Cells ◽  
Stimulation Of

ABSTRACT l-Leucine and 2-ketoisocaproate stimulated insulin release from perifused rat tumoral islet cells (RINm5F line). The secretory response coincided with an increase in the intracellular ATP/ADP ratio, a stimulation of 45Ca outflow from cells perifused in the presence of extracellular Ca2+, and an increase in 32P efflux from cells prelabelled with radioactive orthophosphate. In contrast to d-glucose, however, l-leucine or 2-ketoisocaproate failed to decrease 86Rb outflow, to inhibit 45Ca outflow from cells perifused in the absence of Ca2+ and to enhance the labelling of inositol-containing phospholipids in cells exposed to myo-[2-3H]inositol. These findings suggest that d-glucose, l-leucine and 2-ketoisocaproate exert dissimilar effects on the subcellular distribution of adenine nucleotides and/or 86Rb. The nonmetabolized analogue of l-leucine, 2-aminobicyclo-[2.2.1]heptane-2-carboxylic acid (BCH), also caused an initial stimulation of insulin release and 32P efflux, but this was soon followed by a severe and irreversible inhibition of insulin output, associated with a permanent enhancement of 86Rb outflow. The dual ionic and secretory response to BCH is interpreted in the light of its dual effect on the catabolism of endogenous amino and fatty acids, and raises the view that BCH could be used to interfere with the function of insulinoma cells.

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.

Anion-dependent Mg2+ influx and a role for a vacuolar H+-ATPase in sheep ruminal epithelial cells

2003 ◽  
Vol 285 (1) ◽  
pp. G45-G53 ◽  
Author(s):  
Monika Schweigel ◽  
Holger Martens
Keyword(s):  
Epithelial Cells ◽  
Atpase Activity ◽  
Primary Culture ◽  
Intracellular Ph ◽  
Uptake Rate ◽  
Ruminal Fermentation ◽  
Fermentation Products ◽  
Fluorescence Techniques ◽  
Transport Inhibitors ◽  
Stimulation Of

The K+-insensitive component of Mg2+ influx in primary culture of ruminal epithelial cells (REC) was examined by means of fluorescence techniques. The effects of extracellular anions, ruminal fermentation products, and transport inhibitors on the intracellular free Mg2+ concentration ([Mg2+]i), Mg2+ uptake, and intracellular pH were determined. Under control conditions (HEPES-buffered high-NaCl medium), the [Mg2+]i of REC increased from 0.56 ± 0.14 to 0.76 ± 0.06 mM, corresponding to a Mg2+ uptake rate of 15 μM/min. Exposure to butyrate did not affect Mg2+ uptake, but it was stimulated (by 84 ± 19%) in the presence of [Formula: see text]. In contrast, Mg2+ uptake was strongly diminished if REC were suspended in [Formula: see text]-buffered high-KCl medium (22.3 ± 4 μM/min) rather than in HEPES-buffered KCl medium (37.5 ± 6 μM/min). After switching from high- to low-Cl– solution, [Mg2+]i was reduced from 0.64 ± 0.09 to 0.32 ± 0.16 mM and the [Formula: see text]-stimulated Mg2+ uptake was completely inhibited. Bumetanide and furosemide blocked the rate of Mg2+ uptake by 64 and 40%, respectively. Specific blockers of vacuolar H+-ATPase reduced the [Mg2+]i (36%) and Mg2+ influx (38%) into REC. We interpret this data to mean that the K+-insensitive Mg2+ influx into REC is mediated by a cotransport of Mg2+ and Cl– and is energized by an H+-ATPase. The stimulation of Mg2+ transport by ruminal fermentation products may result from a modulation of the H+-ATPase activity.

cAMP stimulates fluorescent bile acid uptake into hepatocytes by membrane hyperpolarization

1996 ◽  
Vol 270 (2) ◽  
pp. G339-G346 ◽  
Author(s):  
S. Grune ◽  
X. J. Meng ◽  
S. A. Weinman
Keyword(s):  
Bile Acid ◽  
Voltage Clamp ◽  
Uptake Rate ◽  
Direct Consequence ◽  
Acid Uptake ◽  
Net Charge ◽  
Membrane Hyperpolarization ◽  
Whole Cell ◽  
Bile Acid Uptake ◽  
Stimulation Of

Elevation of intracellular adenosine 3',5'-cyclic monophosphate (cAMP) hyperpolarizes hepatocytes and increases the uptake rate of bile acids. The purpose of this study was to determine to what extent these two phenomena are linked. Fluorescent bile acid analogues (FBA) were used to probe bile acid transport into whole cell patch-clamped hepatocytes. Na(+)-dependent uptake of cholyl-nitrobenz-2-oxa-1,3-diazol-4-yl-lysine (C-NBD-L), an FBA with a net charge of -1, was shown to be electrogenic, whereas uptake of cholylglycylamidofluorescein (CGamF), an FBA with a net charge of -2, was neutral. Incubation of hepatocytes with 8-bromo-cAMP (8-BrcAMP; 100 microM) increased the uptake rate of the electrogenically transported FBA by 25% (P = 0.002), but had no effect on the uptake rate of the electroneutrally transported FBA. Microelectrode impalements revealed that 8-BrcAMP or forskolin hyperpolarized hepatocytes by 6-8 mV. To determine if hyperpolarization is responsible for the cAMP-induced increase in uptake rate, cAMP was directly introduced into hepatocytes during whole cell patch clamp under voltage-clamp conditions. As long as voltage clamp was maintained at -30 mV there was no stimulation of C-NBD-L uptake. However, when voltage clamp was terminated by either pipette removal or current clamp, cAMP increased the uptake rate by 25-34% (P < 0.002). In both of these protocols, cAMP had no effect on uptake of the electroneutrally transported FBA, CGamF. Finally, in voltage-clamped hepatocytes in the absence of cAMP, a 10-mV hyperpolarization increased the uptake rate of C-NBD-L by 23%. We therefore conclude that short-term cAMP-induced stimulation of fluorescent bile acid uptake in hepatocytes is a direct consequence of membrane hyperpolarization.

Dual effects of cisapride on gastric emptying and antropyloroduodenal motility

1993 ◽  
Vol 264 (2) ◽  
pp. G195-G201 ◽  
Author(s):  
R. Fraser ◽  
M. Horowitz ◽  
A. Maddox ◽  
J. Dent
Keyword(s):  
Gastric Emptying ◽  
Healthy Volunteers ◽  
Gastric Motility ◽  
Normal Subjects ◽  
Solid Component ◽  
Pressure Waves ◽  
Dual Effect ◽  
Intravenous Saline ◽  
Plausible Mechanism ◽  
Stimulation Of

There is little information about the effects of cisapride on human antropyloroduodenal motility, despite its documented efficacy for increasing the rate of gastric emptying in patients with gastroparesis. Cisapride has been reported to have little effect on gastric emptying in normal subjects. Antral, pyloric, and duodenal pressures were recorded simultaneously with gastric emptying in 20 healthy volunteers. Thirty minutes after the solid component of the meal had started to empty from the stomach, each subject received either 10 mg cisapride i.v. (11 subjects) or intravenous saline (9 subjects). Intravenous saline had no effect on either motility or gastric emptying. In contrast, cisapride administration was associated with a dual effect on motility, with initial suppression of antral pressure waves (P < 0.05) followed by stimulation of associated antropyloroduodenal pressure waves (P < 0.01). Gastric emptying slowed in the first 30 min after cisapride (P < 0.05), and this was followed by more rapid gastric emptying (P < 0.01). The amount of the meal emptied in the 60 min after cisapride correlated with the number of associated antroduodenal pressure waves (r = 0.75, P < 0.001) but not with the number of antral waves (r = 0.42, NS). These results indicate that cisapride in a dose of 10 mg i.v. has dual effects on gastric emptying and gastric motility. The stimulation of associated antral pressure waves is a plausible mechanism for the efficacy of cisapride in the treatment of gastroparesis.

Effect of stimulation with light on synthesis and release of acetylcholine by an isolated mammalian retina

1976 ◽  
Vol 39 (6) ◽  
pp. 1210-1219 ◽  
Author(s):  
R. H. Masland ◽  
C. J. Livingstone
Keyword(s):  
Initial Rate ◽  
Horizontal Cells ◽  
High Rate ◽  
Cholinergic Synapse ◽  
Pharmacological Agents ◽  
Choline Incorporation ◽  
Rate Acceleration ◽  
Mammalian Retina ◽  
Release Of Acetylcholine ◽  
Stimulation Of

1. Acetylcholine synthesis and release were studied in rabbit retinas isolated from the eye and incubated under conditions in which their electrophysiological function is maintained. ACh synthesized from exogenous [14C] choline appeared in the retina at an initial rate of 16 nmol/g wet wt-h. Incorporation of labeled choline into ACh was accelerated by stimulation of the retina with light. 2. Retinas incubated for 40 min in the presence of labeled choline and then superfused with a medium containing an anticholinesterase released radioactive ACh into the perfusate. The rate of release increased approximately fourfold during stimulation with light. 3. When retinas were incubated with labeled choline and then superfused with medium containing no pharmacological agents, stimulation with light caused an increased release of choline into the perfusate. The recovery of labeled choline following stimulation was enhanced by hemicholinium 3. 4. Neither the light-induced release of ACh (in perfusate containing anticholinesterase) nor the light-induced release of choline (in perfusate containing no anticholinesterase) occurred if the perfusate contained 20 mM Mg2+ and 0.2 mM Ca2+. 5. Synthesis of ACh by the retina at a high rate, acceleration of choline incorporation by stimulation, and Ca2+-dependent release of ACh by stimulation are each presumptive evidence that the retina contains a cholinergic synapse. If this presumption is correct, one such synapse mayx be of an amacrine or bipolar cell since these cells can depolarize during illumination, whereas the predominant response of receptor and horizontal cells is hyperpolarization.

Excitation-induced Ca2+uptake in rat skeletal muscle

1999 ◽  
Vol 276 (2) ◽  
pp. R331-R339 ◽  
Author(s):  
H. Gissel ◽  
T. Clausen
Keyword(s):  
Skeletal Muscle ◽  
Electrical Stimulation ◽  
Initial Rate ◽  
Low Frequency ◽  
Channel Blockers ◽  
Ca Uptake ◽  
Edl Muscle ◽  
Isotonic Contractions ◽  
Progressive Accumulation ◽  
Stimulation Of

In isolated rat extensor digitorum longus (EDL) muscle mounted for isometric contractions, chronic low-frequency electrical stimulation was found to lead to an increased uptake of45Ca (154% above control after 240 min) and a progressive accumulation of Ca2+ (85% above control after 240 min). In soleus, however, this treatment led to a small, but significant, increase in 45Ca uptake (30% above control after 180 min) but no significant accumulation of Ca2+. In muscles mounted for isotonic contractions without any external load, electrical stimulation gave rise to a larger45Ca uptake and accumulation of Ca2+ in both EDL and soleus. These uptakes of Ca2+ coincided with an accumulation of Na+. During isometric or isotonic contractions, stimulation at 40 Hz increased the initial (60 s) rate of 45Ca uptake in soleus muscle 15- and 30-fold, respectively. The stimulation-induced increase in 45Ca uptake was only reduced by 17% by the Ca2+-channel blockers nifedipine and verapamil but was blocked by tetrodotoxin. The initial rate of stimulation-induced 22Na and45Ca uptake was correlated ( r = 0.80; P < 0.003). Stimulation of Na+ channels with veratridine increased 45Ca uptake by 93 and 139% in soleus and EDL, respectively ( P < 0.001), effects that were abolished by tetrodotoxin. The results indicate that in skeletal muscle, excitation induces a considerable influx of Ca2+, mediated by Na+ channels.

scholarly journals Rapid formation of inositol 1,3,4,5-tetrakisphosphate and inositol 1,3,4-trisphosphate in rat parotid glands may both result indirectly from receptor-stimulated release of inositol 1,4,5-trisphosphate from phosphatidylinositol 4,5-bisphosphate

1986 ◽  
Vol 238 (2) ◽  
pp. 507-516 ◽  
Author(s):  
P T Hawkins ◽  
L Stephens ◽  
C P Downes
Keyword(s):  
Initial Rate ◽  
Parotid Glands ◽  
Inositol 1,4,5 Trisphosphate ◽  
Rapid Formation ◽  
Inositol Tetrakisphosphate ◽  
Rat Parotid ◽  
Phosphatidylinositol 4 ◽  
Hydrolysis Of ◽  
Direct Hydrolysis ◽  
Stimulation Of

Addition of 1 mM-carbachol to [3H]inositol-labelled rat parotid slices stimulated rapid formation of [3H]inositol 1,3,4,5-tetrakisphosphate, the accumulation of which reached a peak 20 s after stimulation, and then declined rapidly towards a new steady state. The initial rate of formation of inositol 1,3,4,5-tetrakisphosphate was slower than that for inositol 1,4,5-trisphosphate. The radioactivity in [3H]inositol 1,3,4,5-tetrakisphosphate fell quickly in carbachol-stimulated and then atropine-blocked parotid slices, suggesting that it is rapidly metabolized during stimulation. Parotid homogenates rapidly dephosphorylated inositol 1,4,5-trisphosphate, inositol 1,3,4,5-tetrakisphosphate and, less rapidly, inositol 1,3,4-trisphosphate. Inositol 1,3,4,5-tetrakisphosphate was specifically hydrolysed to a compound with the chromatographic properties of inositol 1,3,4-trisphosphate. The only 3H-labelled phospholipids that we could detect in parotid slices labelled with [3H]inositol for 90 min were phosphatidylinositol, phosphatidylinositol 4-phosphate and phosphatidylinositol 4,5-bisphosphate. Parotid homogenates synthesized inositol tetrakisphosphate from inositol 1,4,5-trisphosphate. This activity was dependent on the presence of ATP. We suggest that, during carbachol stimulation of parotid slices, the key event in inositol lipid metabolism is the activation of phosphatidylinositol 4,5-bisphosphate-specific phospholipase C. The inositol 1,4,5-trisphosphate thus liberated is metabolized in two distinct ways; by direct hydrolysis of the 5-phosphate to form inositol 1,4-bisphosphate and by phosphorylation to form inositol 1,3,4,5-tetrakisphosphate and hence, by hydrolysis of this tetrakisphosphate, to form inositol 1,3,4-trisphosphate.

Dyeing Properties of Lac Dyes for Wool, Silk and Nylon

2011 ◽  
Vol 233-235 ◽  
pp. 817-820
Author(s):  
Bo Wei ◽  
Qiu Yuan Chen ◽  
Ren Cheng Tang ◽  
Guo Qiang Chen
Keyword(s):  
Electrostatic Interaction ◽  
Uptake Rate ◽  
Color Fastness ◽  
Dye Uptake ◽  
Amino Groups ◽  
Dyeing Properties ◽  
Initial Uptake Rate ◽  
Dyed Fabrics ◽  
Initial Uptake

The dyeing properties of lac dyes for wool, silk and nylon fibers were investigated, and compared in terms of dependence of dye uptake on pH, dyeing rates, and building-up performance as well as color hue and color fastness of dyed fabrics. For all the three fibers, the uptake of lac dyes was greatly influenced by pH, indicating that the electrostatic interaction between lac dyes and fibers predominantly contributes to lac adsorption. The maximum adsorption wavelength of dyed fabrics shifted to a higher value with increasing application pH, indicating the existence of bathochromic effect. Lac dyes showed the quickest initial uptake rate for silk, the slowest rate for wool. The capacity of lac uptake by three fibers was in the following order: wool > silk > nylon, this being in accord with the quantity of amino groups in these fibers. Dyed wool exhibited the best color fastness.

scholarly journals Metabolic adaptation in phosphorylase kinase deficiency. Changes in metabolite concentrations during tetanic stimulation of mouse leg muscles

1980 ◽  
Vol 186 (1) ◽  
pp. 331-341 ◽  
Author(s):  
Z H Rahim ◽  
D Perrett ◽  
G Lutaya ◽  
J R Griffiths
Keyword(s):  
Initial Rate ◽  
Adenine Nucleotide ◽  
Mass Action ◽  
Metabolic Adaptation ◽  
Phosphorylase Kinase ◽  
Normal Muscle ◽  
Leg Muscles ◽  
Muscle Work ◽  
Muscle Groups ◽  
Stimulation Of

1. Glycogen, nucleotides and glycolytic intermediates and products were measured before and during tetanus in the hamstrings-muscle groups of normal (C3H) and phosphorylase kinase-deficient (ICR/IAn) mice. 2. Phosphorylase kinase-deficient muscles contained 3-4-fold more glycogen and sustained a larger (approx. 2-fold), more rapid (11 +/- 2 ng/s faster) and more prolonged glycogenolysis during 120s tetanus despite their lack of phosphorylase a. 3. No significant change in total adenine nucleotide contents occurred during tetanus in either strain, but there was a 60-100-fold rise in IMP concentration to approx. 2mM in both strains. The initial rate of IMP formation was 6-fold more rapid (112 nmol/s per g) in phosphorylase kinase-deficient muscle. 4. Adenylosuccinate content rose to 36 nmol/g in phosphorylase kinase-deficient muscle and to 9 nmol/g in normal muscle at 45s tetanus, but then fell. 5. In phosphorylase kinase-deficient muscle, glucose 6-phosphate, a powerful phosphorylase inhibitor, was 56% of that in normal muscle. 6. The mass-action ratio of the phosphoglucomutase-catalysed reaction [glucose 6-phosphate]/[glucose 1-phosphate] was markedly lower than Keq. (approx. 17) in relaxed muscle of both strains (approx. 5-7), but rose significantly during tetanus to the value for Keq. 7. The data for IMP satisfy the criteria put forward by Rahim, Perrett & Griffiths [(1976) FEBS Lett. 69, 203-206] for a nucleotide activator of phosphorylase b: it should be present at a higher concentration in phosphorylase kinase-deficient muscle, its concentration should rise during muscle work, and it should attain a concentration comparable with its activation constant for phosphorylase b.

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