scholarly journals The dissociation of exocytosis and respiratory stimulation in leucocytes by ionophores

1976 ◽  
Vol 156 (2) ◽  
pp. 209-213 ◽  
Author(s):  
G Zabucchi ◽  
D Romeo
Keyword(s):  
Oxygen Consumption ◽  
Lactate Dehydrogenase ◽  
Ionophore A23187 ◽  
Polymorphonuclear Leucocytes ◽  
Free Medium ◽  
Alkali Cations ◽  
Experimental Conditions ◽  
Bivalent Cations ◽  
Respiratory Stimulation ◽  
Stimulation Of

By exploiting the unique characteristics of three ionophores, experimental conditions were found which permit the dissociation of respiratory stimulation from secretion in polymorphonuclear leucocytes. A marked stimulation of respiration was produced by ionophore X537A, which binds and transports both alkali-earth and alkali cations. The stimulatory activity of this ionophore was the same at either high or low Na+/K+ ratios in the medium and was virtually unaffected by extracellular Ca2+. A slight stimulation of oxygen consumption was also caused by the K+-selective ionophore valinomycin and by ionophore A23187, which complexes and transfers bivalent cations. Ionophore X537A and valinomycin were unable to stimulate selective release of granuleassociated β-glucuronidase and gradually increased cell fragility, as monitored by increased leakage of lactate dehydrogenase. Ionophore A23187 slightly increased exocytosis of β-glucuronidase. In a Mg2+-free medium, Ca2+, added simultaneously with ionophore A23187, greatly enhanced respiration and secretion of the granule enzyme. If Ca2+ was added a few minutes after the ionophore, exocytosis occurred, but no respiratory burst was observed. If the latter experiment was repeated in the presence of extracellular Mg2+, both secretion and respiration were stimulated. This effect was not produced by Mn2+ or Ba2+. It is proposed that Ca2+ is required for triggering selective secretion of granule enzymes from leucocytes is caused by an intracellular redistribution of cations, which may invovle Mg2+-dependent mechanisms.

VARIOUS EFFECTS OF THYROXINE ANALOGUES ON THE HEART AND SERUM CHOLESTEROL IN THE RAT

1960 ◽  
Vol 21 (1) ◽  
pp. 25-32 ◽  
Author(s):  
G. S. BOYD ◽  
M. F. OLIVER
Keyword(s):  
Heart Rate ◽  
Oxygen Consumption ◽  
Serum Cholesterol ◽  
Rate Ratio ◽  
Heart Weight ◽  
Liver Cholesterol ◽  
Response Curves ◽  
Experimental Conditions ◽  
Cholesterol Levels ◽  
Stimulation Of

SUMMARY A series of twelve iodinated thyroxine analogues was studied for thyro-activity in the rat. Each analogue produced antigoitrogenic activity, increased oxygen consumption, heart rate and heart weight, and decreased serum and liver cholesterol levels. A 'serum cholesterol/heart rate ratio' may be computed for these analogues under fixed experimental conditions. While the dose-response curves for different analogues in any of these assays are rarely parallel, it is, nevertheless, clear that under certain experimental conditions some iodothyronines cause a relatively greater depression of cholesterol levels and less stimulation of heart rate than others. Some of the most active in this respect are DT4, DT3, DT2 and T4F.

Effect of norepinephrine on gluconeogenesis in perfused livers of cold-exposed rats

1985 ◽  
Vol 249 (3) ◽  
pp. E281-E286 ◽  
Author(s):  
M. Shiota ◽  
T. Tanaka ◽  
T. Sugano
Keyword(s):  
Oxygen Consumption ◽  
Cold Exposure ◽  
Plasma Glucose Level ◽  
Glucose Production ◽  
Hepatic Glycogen ◽  
Perfused Liver ◽  
Free Medium ◽  
Adrenergic Response ◽  
Time Periods ◽  
Stimulation Of

The effects of norepinephrine and glucagon on gluconeogenesis were studied in hemoglobin-free perfused liver from rats kept for 1-20 days at 4 degrees C. When rats were starved for 24 h at 4 degrees C, the plasma glucose level of rats exposed to cold for 5, 10, and 20 days was significantly higher than that of rats for 1 day, but hepatic glycogen decreased to the same level in all groups. In the isolated perfused liver, basal rates of oxygen consumption and glucose production increased slightly through 5 days of cold exposure and returned to control levels after 20 days of cold exposure. The rates of glucose production from lactate, pyruvate, sorbitol, and glycerol increased by 20-30% after 5 days of cold exposure. The stimulation of gluconeogenesis from these substrates by norepinephrine and phenylephrine increased markedly at all time periods from 1 to 20 days in the cold, with a maximum at 5 days. The stimulation of glycogenolysis by norepinephrine was not affected by cold exposure. The response to catecholamines decreased markedly in liver perfused with calcium-free medium and/or with phentolamine. The stimulation of gluconeogenesis by glucagon increased only in rats exposed to cold for 20 days. The results obtained suggest that the stimulation of hepatic gluconeogenesis by cold is due to an alpha-adrenergic response, and the activation occurs beyond the interaction of norepinephrine with its receptor.

Effect of the ionophore A23187 on chloride transport across isolated frog cornea

1977 ◽  
Vol 233 (2) ◽  
pp. F94-F101
Author(s):  
O. A. Candia ◽  
R. Montoreano ◽  
S. M. Podos
Keyword(s):  
Chloride Transport ◽  
Ringer Solution ◽  
Ionophore A23187 ◽  
Free Medium ◽  
Intracellular Ca ◽  
Adrenergic Blockers ◽  
Relative Inhibition ◽  
Stimulation Of ◽  
Frog Cornea ◽  
Cl Permeability

The ionophore A23187 at a concentration of 10(-7) to 10(-5) M stimulated active transport of Cl across the isolated frog cornea. The ionophore had no effect in a Cl-free medium. Both unidirectional Cl fluxes were increased by A23187. The electrical resistance was decreased, and this can be totally accounted for by the increment in passive Cl fluxes. The effect of A23187 on Cl transport and permeability mimicked the effects of cyclic AMP, isoproterenol, and epinephrine. A23187 had no effect when the corneas were fully stimulated by epinephrine or isoproterenol. A23187 produced normal stimulation of the SCC in corneas pretreated with alpha- and beta-adrenergic blockers. The stimulation of the SCC by A23187 was dependent on the presence of Ca in the Ringer solution. Excess Ca (10 mM) resulted in a reduced response. Increasing the Mg concentration in the medium reduced the stimulation of the SCC with Ca concentrations of 0.1-5 mM, but prevented the relative inhibition of 10 mM Ca. Intracellular Ca concentration seemed to regulate Cl permeability of the cornea.

Cholinergic stimulation of ouabain-sensitive respiration in rat submandibular gland

1983 ◽  
Vol 245 (3) ◽  
pp. G364-G368 ◽  
Author(s):  
D. J. Stewart ◽  
D. J. Pon ◽  
A. K. Sen
Keyword(s):  
Oxygen Consumption ◽  
Submandibular Gland ◽  
Sodium Pump ◽  
Calcium Ionophore ◽  
Sodium Reabsorption ◽  
Tissue Respiration ◽  
Ionophore A23187 ◽  
Cholinergic Stimulation ◽  
Rat Submandibular Gland ◽  
Stimulation Of

Oxygen consumption of slices of rat submandibular gland was monitored with an oxygen electrode method. Carbachol stimulated an immediate increase in tissue respiration that was inhibitable by ouabain. The stimulation required the presence of calcium in the incubation medium and was blocked by atropine. The calcium ionophore A23187 also stimulated ouabain-sensitive oxygen consumption in the tissue slices. The results show that the mechanism using the extra energy during cholinergic stimulation is the sodium pump. Amiloride at a 1, 10, or 100 microM concentration had no effect on stimulation of ouabain-sensitive respiration by carbachol. Since amiloride, which is known to block the sodium reabsorption process in the ductal segment, has no effect on the stimulation, the increased sodium pump activity is probably located in the acinar region and is associated with the primary fluid secretion process.

Passive K+-Cl- fluxes in low-K+ sheep erythrocytes: modulation by A23187 and bivalent cations

1985 ◽  
Vol 249 (3) ◽  
pp. C271-C278 ◽  
Author(s):  
P. K. Lauf
Keyword(s):  
Complete Inhibition ◽  
Cell Swelling ◽  
Ionophore A23187 ◽  
Tetraacetic Acid ◽  
Sheep Erythrocytes ◽  
Cl Transport ◽  
Bivalent Cations ◽  
Low K ◽  
O 10 ◽  
Stimulation Of

A fraction of the ouabain-resistant (OR) K+ flux of low-K+ (LK) sheep erythrocytes is Cl- dependent (K+-Cl- transport) and is activated reversibly by cell swelling or irreversibly by treatment with N-ethylmaleimide (NEM). The effect of the ionophore A23187 plus bivalent cations (Me2+) or ethyleneglycol-bis(beta-aminoethylether)-N,N'-tetraacetic acid (EGTA) was studied on K+-Cl- transport in control or NEM-treated LK cells. The following observations were made. 1) A23187 (6 microM), at a hematocrit of 10% (vol/vol) and in the presence of 1 mM EGTA, activated severalfold OR K+-Cl- transport in shrunken or swollen cells but failed to stimulate further K+-Cl- flux in NEM-treated cells. 2) In the absence of EGTA, but at very low external Ca2+ concentrations [( Ca2+]o = 10(-7) M), A23187 stimulated OR K+-Cl- flux in controls less than with EGTA and inhibited it slightly in NEM-treated cells. 3) When [Ca2+]o was raised to 10(-3) M, an almost complete inhibition of OR K+-Cl- fluxes occurred in shrunken, swollen, or NEM-treated cells. 4) Other Me2+ inhibited OR K+-Cl- flux in the presence of A23187 in the following order of decreasing potency: Mn2+ much greater than Ca2+ greater than Mg2+ greater than Sr2+ much much greater than Ba2+. 5) Stimulation of OR K+-Cl- flux by A23187 +/- EGTA and inhibition by A23187 + Ca2+ were reversible and did not alter significantly cellular ATP. 6) The stimulatory effect of A23187 plus EGTA, perhaps by Me2+ removal, on K+-Cl- flux and its inhibition by Ca2+ were reversibly abolished in metabolically depleted cells.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals The response to monochromatic light flashes of the oxygen consumption of honeybee drone photoreceptors.

1987 ◽  
Vol 89 (5) ◽  
pp. 791-813 ◽  
Author(s):  
G J Jones ◽  
M Tsacopoulos
Keyword(s):  
Oxygen Consumption ◽  
Time Course ◽  
Monochromatic Light ◽  
Action Spectrum ◽  
Photoreceptor Cells ◽  
Inhibitory Effect ◽  
Experimental Conditions ◽  
Honeybee Drone ◽  
Light Flashes ◽  
Stimulation Of

Local measurements of the fall in oxygen pressure on stimulation of slices of the retina of the honeybee drone by flashes of light were made with oxygen microelectrodes and used to calculate the kinetics of the extra oxygen consumption (delta QO2) induced by each flash. The action spectrum for delta QO2 was obtained from response-intensity curves in response to brief (40 ms) monochromatic light flashes. The action spectrum of receptor potentials was obtained with the same experimental conditions. The two action spectra match closely: they deviate slightly from the photosensitivity spectrum of the drone rhodopsin (R). The deviation is thought to be due to wavelength-dependent light scattering and absorption in the preparation. In these experiments, the visual pigment was first illuminated with orange light, which is known to convert the bistable drone photopigment predominantly to the R state from the metarhodopsin (M) state. When long (300-900 ms) light flashes were used to elicit delta QO2, the responses to different wavelengths could not be matched in time course (as for the short flashes). Flashes producing large R-to-M conversions produced a prolonged delta QO2. The prolongation did not occur after double flashes, which produced both large R-to-M and M-to-R conversions. Similar changes in the length of afterpotentials in the photoreceptor cells and in a long-lasting decrease in photoreceptor intracellular K+ activity were found after long single or double flashes. The results are interpreted to show that the initial event for stimulation by light of metabolism in the drone retina is the same as that for stimulation of electrical responses (i.e., absorption of photons by R). Absorption of photons by M can produce an inhibitory effect on this stimulation.

Effects of methylprednisolone on the energy metabolism of quiescent and conA-stimulated thymocytes of the rat

1993 ◽  
Vol 13 (1) ◽  
pp. 41-52 ◽  
Author(s):  
Frank Buttgereit ◽  
Martin D. Brand ◽  
Marianne Müller
Keyword(s):  
Plasma Membrane ◽  
Oxygen Consumption ◽  
Energy Metabolism ◽  
Concanavalin A ◽  
Glucocorticoid Receptors ◽  
High Concentrations ◽  
Subsequent Activation ◽  
Respiratory Stimulation ◽  
Stimulation Of

The short-term effects of high concentrations of Methylprednisolone (MP) on the energy metabolism of quiescent and Concanavalin A-stimulated rat thymocytes were investigated in vitro. Concanavalin A (ConA) stimulated the respiration rate of quiescent thymocytes by 35%. Addition of more than 0.15 mg MP/107 cells to ConA-stimulated cells reversed this respiratory stimulation; in addition, higher concentrations of MP caused a similar progressive decrease in the rate of respiration of both quiescent and ConA-stimulated cells. Similarly, the stimulation of respiration by ConA was greatly reduced in MP-treated cells. MP addition lowered cytoplasmic [Ca2+] and, at high concentrations, abolished the ability of ConA to increase [Ca2+]. Thus MP both reverses and prevents the immediate stimulation of thymocytes by ConA. In quiescent thymocytes, MP strongly inhibited that part of the oxygen consumption used to drive the cycle of Na+ influx across the plasma membrane and Na+ efflux on the Na+K+-ATPase, but did not inhibit oxygen consumption used to drive protein synthesis. In ConA-stimulated thymocytes MP had the same effects and also strongly inhibited oxygen consumption dependent on the cycle of Ca2+ influx across the plasma membrane and Ca2+ efflux on the Ca2+-ATPase, but had little effect on oxygen consumption used to drive RNA and DNA synthesis. These results show that MP prevents cation cycling in thymocytes (either by preventing cation influx or by inhibiting cation pumps) and prevents mitogenic stimulation of the cells. The high MP concentration required and the speed of onset of the effect (lless than 30s) provide strong evidence that these effects of MP are not mediated by glucocorticoid receptors and subsequent activation of gene expression. They may be caused by direct effects of MP on the properties of the plasma membrane. These effects are considered to be, at least partially, responsible for the beneficial results that currently have been obtained using MP megadoses in various clinical situations.

scholarly journals STUDIES ON CELL METABOLISM AND CELL DIVISION

1936 ◽  
Vol 20 (2) ◽  
pp. 173-184 ◽  
Author(s):  
M. E. Krahl ◽  
G. H. A. Clowes
Keyword(s):  
Oxygen Consumption ◽  
Cell Division ◽  
Cell Metabolism ◽  
Substituted Phenols ◽  
Experimental Conditions ◽  
Arbacia Punctulata ◽  
Oxidation Reduction ◽  
Rate Of Oxygen Consumption ◽  
Considerable Support ◽  
Stimulation Of

The dihalo and trihalophenols, and phenols containing both halo and nitro substituents in the same molecule, produce, in fertilized eggs of Arbacia punctulata, a rise in rate of oxygen consumption and a reversible block to cell division. To define the conditions which affect the degree of this activity, the following factors have been varied: the arrangement of substituents in the molecule, the concentration of reagent, and the time after fertilization at which the reagent is added. The stimulation of oxygen consumption and reversible block to cell division produced by the dihalophenols are qualitatively the same as those previously produced in fertilized Arbacia eggs by certain dinitrophenols. To yield optimum respiratory effect and maximum division block, it usually requires a higher concentration of dihalo than of the corresponding dinitrophenol. For example, with fertilized Arbacia eggs at 20°C. 2,4-dinitrophenol, in optimum concentration of 3 x 10–5 molar, raises oxygen consumption to 292 per cent of normal (4). The corresponding values for two dihalo analogues are: 2,4-dichlorophenol, 10–4 molar and 236 per cent; 2,4-dibromophenol, 6 x 10–5 molar and 282 per cent. The halophenols differ from the nitrophenols in two interesting respects: (a) The monohalophenols produce little or no oxidative stimulation or division block in fertilized Arbacia eggs; p-nitrophenol is very active in both respects. (b) The symmetrical trihalophenols have an appreciable ability to stimulate oxygen consumption and block division; symmetrical trinitrophenol is inactive in both respects (4). The increases in oxygen consumption produced in fertilized Arbacia eggs by 2,4-dichloro and 2,4-dinitrophenol are larger than the percentage increases given by methylene blue and o-cresol indophenol under the same experimental conditions. The dihalo and dinitrophenols produce a reversible block to the cell division of fertilized marine eggs. The oxidation-reduction indicators, in contrast to the dihalo and dinitrophenols, block cell division irreversibly and fertilized eggs of Arbacia do not recover from optimum respiratory stimulating concentrations of these oxidation-reduction dyes. The present experiments with halophenols are in harmony with and lend considerable support to the hypothesis (4) that nitro and similarly substituted phenols derive their biological activity from the presence and properties of the phenolic OH group, as modified by proper substitution in the phenolic benzene ring.

Interaction of Vasopressin with Human Blood Platelets: Dependency on Mg2+

1986 ◽  
Vol 56 (03) ◽  
pp. 260-262 ◽  
Author(s):  
Isabella Roos ◽  
Fabrizia Ferracin ◽  
Alfred Pletscher
Keyword(s):  
Phosphatidic Acid ◽  
Human Blood ◽  
Arginine Vasopressin ◽  
Specific Binding ◽  
Blood Platelets ◽  
Bivalent Cations ◽  
Platelet Membranes ◽  
Maximal Rise ◽  
Human Blood Platelets ◽  
Stimulation Of

SummaryArginine-vasopressin (AVP) in the presence of Mg2+ but not in the absence of bivalent cations led to accumulation of [32P]-phosphatidic acid ([32P]-PA) in human blood platelets. Mg2+ also enhanced the specific binding of [3H]-AVP to intact platelets. The concentrations of the cation which enabled AVP to cause half maximal rise of [32P]-PA and those inducing half maximal [3H]-AVP-binding were of the same order. It is concluded that the stimulation of phosphatidyl inositide breakdown by AVP in presence of Mg2+ is at least partially due to a Mg2+-induced enhancement of specific AVP-binding to the platelet membranes.

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