scholarly journals A cytosolic sperm factor triggers calcium oscillations in rat hepatocytes

1996 ◽  
Vol 313 (2) ◽  
pp. 369-372 ◽  
Author(s):  
Christopher P. BERRIE ◽  
K. S. Roy CUTHBERTSON ◽  
J. PARRINGTON ◽  
F. Anthony LAI ◽  
Karl SWANN
Keyword(s):  
Rat Hepatocytes ◽  
Calcium Oscillations ◽  
Dorsal Root Ganglion Neurons ◽  
Protein Factor ◽  
Mammalian Sperm ◽  
Low Concentrations ◽  
Sperm Factor ◽  
High Concentrations ◽  
Ganglion Neurons ◽  
Free Media

Previously it has been shown that injecting a cytosolic sperm protein factor into mammalian eggs induces sustained repetitive transients of cytosolic free Ca2+ ([Ca2+]i), or [Ca2+]i oscillations [Swann (1990) Development 110, 1295-1302]. These sperm-factor (SF)-induced [Ca2+]i oscillations are similar to those seen at fertilization. Here we demonstrate that injecting the same cytosolic extracts of mammalian sperm into single rat hepatocytes induces a series of [Ca2+]i oscillations, as measured by aequorin luminescence. SF injection into hepatocytes induced [Ca2+]i oscillations that were of longer duration, lower frequency and greater amplitude than those seen with the Ins(1,4,5)P3-generating agonist phenylephrine. The SF-induced [Ca2+]i responses appeared to be due to internal release of Ca2+, since transients could occur in Ca2+-free media. Addition of the phorbol ester phorbol 12,13-dibutyrate (PDBu) at low concentrations did not inhibit the SF-induced [Ca2+]i oscillations; high concentrations of PDBu led to a sustained increase in [Ca2+]i concentrations. These data demonstrate that sperm contain a protein factor capable of inducing a characteristic series of [Ca2+]i oscillations in a somatic cell, the hepatocyte. Along with previous observations in dorsal root ganglion neurons, the data suggest a widespread efficacy of the factor in triggering Ca2+ oscillations.

Mechanisms of ouabain-induced arterial muscle contraction

1980 ◽  
Vol 239 (2) ◽  
pp. H199-H205 ◽  
Author(s):  
N. Toda
Keyword(s):  
Muscle Contraction ◽  
Contractile Response ◽  
Cerebral Arteries ◽  
Peripheral Arteries ◽  
Femoral Arteries ◽  
Low Concentrations ◽  
Electrogenic Na Pump ◽  
High Concentrations ◽  
Free Media ◽  
Alpha Antagonist

Ouabain caused dose-related contractions in helically cut strips of cerebral, mesenteric, renal, and femoral arteries isolated from dogs and monkeys; the contractions were elicited at lower concentrations in cerebral than in the peripheral arteries. Contractions induced by ouabain were abolished by exposure of cerebral arteries to Ca2+-free media. Contractions induced by Ca2+ in Ca2+-free media were potentiated by ouabain. Substitution of LiCl for NaCl and reduction of [K+]0 suppressed the contractile response of cerebral arteries to ouabain. Pretreatment of dogs with reserpine abolished the response of peripheral arteries to ouabain but not the cerebroarterial response. Phentolamine also abolished the response of peripheral arteries. Once oubain-induced contractions were stabilized, the alpha-antagonist caused a marked relaxation in peripheral but not in cerebral arteries. Ouabain-induced contractions appear to be mediated by an increase in the Ca2+ influx that results mainly from an inhibition of the electrogenic Na+ pump in low concentrations (cerebral arteries) and from a release of norepinephrine from nerves in high concentrations (mesenteric, renal, and femoral arteries).

Effects of cytochalasin B on the aggregation, electrophoretic mobility and surface morphology of chick neural retina cells

1975 ◽  
Vol 17 (3) ◽  
pp. 371-379
Author(s):  
G.E. Jones
Keyword(s):  
Surface Morphology ◽  
Electrophoretic Mobility ◽  
Cytochalasin B ◽  
Neural Retina ◽  
Initial Rise ◽  
Low Concentrations ◽  
Significant Difference ◽  
Site Of Action ◽  
High Concentrations ◽  
Free Media

Over a concentration range of o-5-10 mug/cm-3, cytochalasin B caused a biphasic change in the electrophoretic mobility of disaggregated neural retina cells. An initial rise in anodal mobility at low concentrations of the drug was transformed into a reduction in the mobility below that of the control at a concentration of 10 mug/cm-3. The effect of cytochalasin B was found to be reversible by washing treated cells in cytochalasin B-free media. This was investigated at a concentration of cytochalasin at which the greatest difference existed between the mobilities of the control and experimental cell suspensions. Reaggregation of cell dispersions failed to show any significant difference in the rate of aggregation between cytochalasin B-treated cells and the control. Scanning electron microscopy of cells fixed while in suspension also showed little significant change in the surface morphology upon application of cytochalasin B. In high concentrations of the drug cells appeared somewhat smoother in outline, but no correlation was found between changes in surface morphology and the variations in cell electrophoretic mobility. It is concluded that the observed changes in electrophoretic mobility may be attributed to a binding of cytochalasin B to the cell membrane. This lends support to the hypothesis that the primary site of action of cytochalasin B may be the plasma membrane.

Dual effect of deferoxamine on free radical formation and reoxygenation injury in isolated hepatocytes

1995 ◽  
Vol 269 (1) ◽  
pp. G132-G137
Author(s):  
P. Caraceni ◽  
D. H. Van Thiel ◽  
A. B. Borle
Keyword(s):  
Lipid Peroxidation ◽  
Cell Injury ◽  
Rat Hepatocytes ◽  
Iron Chelator ◽  
Isolated Hepatocytes ◽  
Dual Effect ◽  
Enhanced Chemiluminescence ◽  
Low Concentrations ◽  
Ldh Release ◽  
High Concentrations

The effects of low concentrations (10 and 100 microM) and high concentrations (1, 10, and 20 mM) of deferoxamine (DFO) on superoxide (O2-.) formation, lipid peroxidation, and cell injury were studied in freshly isolated perfused rat hepatocytes during a 2-h reoxygenation period after 2.5 h of anoxia. O2-. production was measured by lucigenin-enhanced chemiluminescence, lipid peroxidation by malondialdehyde (MDA) formation, and cell injury by lactate dehydrogenase (LDH) release. On reoxygenation and in the absence of DFO, O2-. generation increased 11-fold, MDA increased 3.7-fold, and LDH release practically doubled. Low concentrations of DFO had no effect on O2-. generation but decreased MDA and LDH release from 44 to 75%. High concentrations of DFO significantly depressed O2-. formation, with very little additional effect on MDA or LDH release. These experiments illustrate in a biological system the dual effect of DFO: 1) at low Concentrations, DFO acts as a specific iron chelator and inhibits lipid peroxidation and cell injury without preventing O2-. formation, and 2) at high concentrations, DFO acts as a nonspecific scavenger of oxygen free radicals such as O2-.

Role of calcium fluxes in the action of glucagon on glucose metabolism in rat hepatocytes

1993 ◽  
Vol 265 (1) ◽  
pp. G35-G42 ◽  
Author(s):  
T. Mine ◽  
I. Kojima ◽  
E. Ogata
Keyword(s):  
Glucose Metabolism ◽  
Calcium Influx ◽  
Rat Hepatocytes ◽  
Extracellular Calcium ◽  
Free Calcium ◽  
Isolated Rat Hepatocytes ◽  
Calcium Fluxes ◽  
Low Concentrations ◽  
High Concentrations

The aim of the present study was to assess the role of calcium fluxes in the action of glucagon on glycogenolysis and gluconeogenesis in isolated rat hepatocytes. Calcium influx was blocked by two ways: by use of the compound tetramethrin and by reduction of extracellular calcium to 1 microM. The minimal concentration of tetramethrin that inhibited glucagon-mediated calcium entry was 7.5 x 10(-7) M. In the presence of 7.5 x 10(-7) M tetramethrin, glucagon-induced glycogenolysis was markedly attenuated when glucagon concentration was 10(-9) M or higher. In contrast, tetramethrin had no effect on glucogenolysis evoked by lower concentrations of glucagon. Similarly, tetramethrin greatly reduced gluconeogenesis induced by high concentrations of glucagon without affecting the effect of low concentrations of glucagon. The same results were obtained in the presence of 1 microM extracellular calcium. To abolish glucagon-induced elevation of cytoplasmic free calcium concentration, we heavily loaded quin2 into hepatocytes. In these cells, glycogenolysis evoked by low concentrations of glucagon was completely abolished. Glycogenolysis caused by high concentrations of glucagon was markedly inhibited. These results indicate that glucagon action on hepatic glucose metabolism is mediated by two different mechanisms, which depend on concentrations of glucagon.

scholarly journals Cytosolic free Ca2+ oscillations induced by diadenosine 5′,5′′′-P1,P3-triphosphate and diadenosine 5′,5′′′-P1,P4-tetraphosphate in single rat hepatocytes are indistinguishable from those induced by ADP and ATP respectively

1995 ◽  
Vol 310 (2) ◽  
pp. 629-635 ◽  
Author(s):  
A K Green ◽  
P H Cobbold ◽  
C J Dixon
Keyword(s):  
Cyclic Amp ◽  
Short Duration ◽  
Phorbol Ester ◽  
Individual Cell ◽  
Rat Hepatocytes ◽  
Low Concentrations ◽  
High Concentrations ◽  
The Individual ◽  
Single Response

Diadenosine 5′,5‴-P1,P3-triphosphate (Ap3A) and diadenosine 5′,5‴-P1,P4-tetraphosphate (Ap4A) induce distinctive patterns of [Ca2+]i oscillations in single rat hepatocytes. We show here that [Ca2+]i oscillations induced by Ap3A and ADP are indistinguishable and that [Ca2+]i oscillations induced by Ap4A closely resemble those induced by ATP. These similarities embrace the following: (1) ADP and Ap3A invariably induce [Ca2+]i transients of short duration (approx. 9 s). Ap4A, like ATP, can induce, depending upon the individual cell, either transients of short duration (approx. 9 s), transients of much longer duration or a mixture of short and long transients within a single response. We show here that the pattern of oscillations induced by Ap4A is similar to that induced by ATP in the same hepatocyte. (2) Elevated intracellular cyclic AMP concentration modulates Ap3A-induced transients, like ADP-induced transients, through an increase in both the peak [Ca2+]i and the frequency of the transients. In contrast, Ap4A-induced transients, like ATP-induced transients, develop an increased duration or a sustained rise in [Ca2+]i, with no rise in peak [Ca2+]i. (3) Ap3A-induced transients, like ADP-induced transients, are abolished by low concentrations of the phorbol ester 4 beta-phorbol 12,13-dibutyrate (PDB; 5-10 nM), whereas long Ap4A-induced transients, like long ATP-induced transients, are refractory to high concentrations of PDB (100 nM). We propose that the [Ca2+]i oscillations induced in rat hepatocytes by Ap3A are mediated by the same purinoceptor that mediates the effects of ADP, whereas the oscillations induced by Ap4A are mediated by the same purinoceptor(s) that mediate the effects of ATP.

Neutrophil Elastase Potentiates Cathepsin G-lnduced Platelet Activation

1992 ◽  
Vol 68 (05) ◽  
pp. 570-576 ◽  
Author(s):  
Mary A Selak
Keyword(s):  
Neutrophil Elastase ◽  
Cell Activation ◽  
Thromboxane A2 ◽  
Creatine Phosphate ◽  
Dense Granule ◽  
Cathepsin G ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Low Concentrations ◽  
High Concentrations

SummaryWe have previously demonstrated that human neutrophil cathepsin G is a strong platelet agonist that binds to a specific receptor. This work describes the effect of neutrophil elastase on cathepsin G-induced platelet responses. While platelets were not activated by high concentrations of neutrophil elastase by itself, elastase enhanced aggregation, secretion and calcium mobilization induced by low concentrations of cathepsin G. Platelet aggregation and secretion were potentiated in a concentration-dependent manner by neutrophil elastase with maximal responses observable at 200 nM. Enhancement was observed when elastase was preincubated with platelets for time intervals of 10–60 s prior to addition of a low concentration of cathepsin G and required catalytically-active elastase since phenylmethanesulphonyl fluoride-inhibited enzyme failed to potentiate cell activation. Neutrophil elastase potentiation of platelet responses induced by low concentrations of cathepsin G was markedly inhibited by creatine phosphate/creatine phosphokinase and/or indomethacin, indicating that the synergism between elastase and cathepsin G required the participation of ADP and thromboxane A2. On the other hand, platelet responses were not attenuated by the PAF antagonist BN 52021, signifying that PAF-acether did not play a role in elastase potentiation. At higher concentrations porcine pancreatic elastase exhibits similar effects to neutrophil elastase, demonstrating that the effect of elastase was not unique to the neutrophil protease. While neutrophil elastase failed to alter the ability of cathepsin G to hydrolyze a synthetic chromogenic substrate, preincubation of platelets with elastase increased the apparent affinity of cathepsin G binding to platelets. In contrast to their effect on cathepsin G-induced platelet responses, neither neutrophil nor pancreatic elasatse potentiated aggregation or dense granule release initiated by ADP, PAF-acether, arachidonic acid or U46619, a thromboxane A2 mimetic. Moreover, unlike its effect on cathepsin G, neutrophil elastase inhibited thrombin-induced responses. The current observations demonstrate that elastase can potentiate platelet responses mediated by low concentrations of cathepsin G, suggesting that both enzymes may function synergistically to activate platelets under conditions where neutrophil degranulation occurs.

In Vitro Effects of Ethanol on Rabbit Platelet Aggregation, Secretion of Granule Contents, and Cyclic AMP Levels in the Presence of Prostacyclin

1989 ◽  
Vol 61 (02) ◽  
pp. 254-258 ◽  
Author(s):  
Margaret L Rand ◽  
Peter L Gross ◽  
Donna M Jakowec ◽  
Marian A Packham ◽  
J Fraser Mustard
Keyword(s):  
Cyclic Amp ◽  
Inhibitory Effect ◽  
Rabbit Platelet ◽  
Inhibitory Effects ◽  
Low Concentrations ◽  
Rabbit Platelets ◽  
High Concentrations ◽  
In Vitro Effects ◽  
Aggregation Of Platelets

SummaryEthanol, at physiologically tolerable concentrations, inhibits platelet responses to low concentrations of collagen or thrombin, but does not inhibit responses of washed rabbit platelets stimulated with high concentrations of ADP, collagen, or thrombin. However, when platelet responses to high concentrations of collagen or thrombin had been partially inhibited by prostacyclin (PGI2), ethanol had additional inhibitory effects on aggregation and secretion. These effects were also observed with aspirin- treated platelets stimulated with thrombin. Ethanol had no further inhibitory effect on aggregation of platelets stimulated with ADP, or the combination of ADP and epinephrine. Thus, the inhibitory effects of ethanol on platelet responses in the presence of PGI2 were very similar to its inhibitory effects in the absence of PGI2, when platelets were stimulated with lower concentrations of collagen or thrombin. Ethanol did not appear to exert its inhibitory effects by increasing cyclic AMP above basal levels and the additional inhibitory effects of ethanol in the presence of PGI2 did not appear to be brought about by further increases in platelet cyclic AMP levels.

Aggregation of Cat Platelets in Vitro

1970 ◽  
Vol 23 (03) ◽  
pp. 601-620 ◽  
Author(s):  
Th. B Tschopp
Keyword(s):  
Adenosine Monophosphate ◽  
Blood Collection ◽  
Base Line ◽  
Reversible Aggregation ◽  
Low Concentrations ◽  
Irreversible Aggregation ◽  
High Concentrations ◽  
Two Phases ◽  
Improved Technique

SummaryAggregation of cat platelets in the citrated plasma is examined by means of Born’s absorptiometer. A marked tendency of the platelets of this species to spontaneous aggregation necessitated first of all the development of an improved technique of blood collection.A hypothesis according to which 5-HT is released from the platelets, explains the absence of oscillations on the base line of the absorptiometer, the absence of platelet swelling, when ADP is added, and the effect of stirring on the aggregation curves in cat PRP. The average volume of cat platelets amounts to 10.46 μ3 when directly fixed in the blood, when fixed from PRP to 12.17 μ3, when fixed from stirred PRP to 13.51 μ3.In low concentrations (0.3-2 μM) ADP produce reversible aggregation; in narrowly restricted, individually dissimilar mean concentrations irreversible aggregation in two phases and in high concentrations, irreversible aggregation in one phase. Like ADP serotonin produces 2 phase irreversible aggregation in concentrations of 3-10 μM, but unlike ADP, the aggregation velocity decreases again with high 5-HT concentrations (>100 μM). Adrenaline does not produce aggregation and it is likely that adenosine and adenosine monophosphate inhibit the aggregation by serotonin but not by ADP. Species differences in the aggregation of human, rabbit and cat platelets are discussed.

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