scholarly journals Thapsigargin inhibits voltage-activated calcium channels in adrenal glomerulosa cells

1993 ◽  
Vol 296 (2) ◽  
pp. 309-312 ◽  
Author(s):  
M F Rossier ◽  
C P Python ◽  
M M Burnay ◽  
W Schlegel ◽  
M B Vallotton ◽  
...  
Keyword(s):  
Cell Types ◽  
Inhibitory Effect ◽  
Zona Glomerulosa ◽  
High Threshold ◽  
Patch Clamp Technique ◽  
Dual Effect ◽  
Blocking Voltage ◽  
Current Voltage ◽  
Glomerulosa Cells ◽  
Ca2 Channels

Thapsigargin, an inhibitor of the microsomal Ca2+ pumps, has been extensively used to study the intracellular Ca2+ pool participating in the generation of the agonist-induced Ca2+ signal in various cell types. A dual effect of this agent was observed in bovine adrenal zona glomerulosa cells. At nanomolar concentrations, thapsigargin stimulated a sustained Ca2+ influx, probably resulting from Ca(2+)-store depletion. In contrast, when added at micromolar concentrations, thapsigargin prevented the rise in cytosolic free Ca2+ concentration ([Ca2+]c) induced by K+. This inhibitory effect of thapsigargin on voltage-activated Ca2+ channels was confirmed by measuring Ba2+ currents by the patch-clamp technique. Both low-threshold (T-type) and high-threshold (L-type) Ca2+ channels were affected by micromolar concentrations of thapsigargin. Analysis of the current-voltage relationship for T-type channels revealed that thapsigargin did not modify the sensitivity of these channels to the voltage, but decreased the maximal current flowing through the channels. In conclusion, thapsigargin appears to exert a dual effect on adrenal glomerulosa cells. At lower concentrations, this agent induces a sustained Ca2+ entry, whereas at higher concentrations it decreases [Ca2+]c by blocking voltage-activated Ca2+ channels.

Effects of Inhalational Anesthetics on L-type Ca2+Currents in Human Atrial Cardiomyocytes during β-Adrenergic Stimulation

2003 ◽  
Vol 99 (1) ◽  
pp. 90-96 ◽  
Author(s):  
Jens Fassl ◽  
Christian R. Halaszovich ◽  
Rocco Hüneke ◽  
Eberhard Jüngling ◽  
Rolf Rossaint ◽  
...  
Keyword(s):  
Minimum Alveolar Concentration ◽  
Direct Effects ◽  
Adrenergic Stimulation ◽  
Patch Clamp Technique ◽  
Dual Effect ◽  
Cardiac Side Effects ◽  
Atrial Cardiomyocytes ◽  
Channel Regulation ◽  
Ca2 Channels ◽  
Peak Value

Background Anesthetics may cause cardiac side effects by their action on L-type Ca2+ channels. Direct effects on the channels have not yet been discriminated from an interference with the beta-adrenergic channel regulation. The authors therefore studied the effects of halothane, sevoflurane, and xenon on human cardiac Ca2+ currents during stimulation with isoproterenol. Methods Currents through L-type Ca2+ channels were measured with the patch clamp technique in atrial cardiomyocytes obtained from patients undergoing cardiac surgery. Cells were superfused with solutions equilibrated with anesthetics at the desired concentrations. Ca2+ currents during pulses to 10 mV were evaluated with respect to their peak value (I(max)) and to the total moved charge (Q). Results In the absence and in the presence of isoproterenol (1 microm), sevoflurane (0.29 mm, 1 minimum alveolar concentration [MAC]) significantly depressed Q by 37.8 +/- 7.2% (mean +/- SD) and 40.8 +/- 10.3%, respectively. I(max) was not significantly affected in comparison with control cells never exposed to an anesthetic. Xenon (65%, 1 MAC) did not evoke significant effects. Exposure to halothane (0.39 mm, 1 MAC) during stimulation with isoproterenol significantly reduced Q by 31.3 +/- 23.3% (but not I(max)). After washout of halothane, Q was increased above the level prior to the application of halothane. Moreover, whereas Q promptly declined to baseline levels after washout of isoproterenol in controls, the previous exposure to halothane markedly delayed this decline, leaving Q significantly elevated for several minutes. Conclusions Halothane exerts a dual effect on Ca2+ currents. The long-lasting stimulatory effect may contribute to the proarrhythmic potency of the drug that exceeds that of sevoflurane, which only depressed Ca2+ currents.

scholarly journals Autocrine role of adrenomedullin in the human adrenal cortex

2001 ◽  
Vol 170 (1) ◽  
pp. 259-265 ◽  
Author(s):  
LM Thomson ◽  
S Kapas ◽  
M Carroll ◽  
JP Hinson
Keyword(s):  
Cell Line ◽  
Second Messenger ◽  
Cell Types ◽  
Zona Glomerulosa ◽  
Adrenocortical Cell ◽  
Gene Encoding ◽  
Calcitonin Gene ◽  
H295r Cells ◽  
Glomerulosa Cells

Previous studies from our laboratory have reported that adrenomedullin is synthesised in rat zona glomerulosa cells. In the present studies, it was found that the human adrenocortical cell line H295R expresses the gene encoding adrenomedullin, and that immunoreactive adrenomedullin is released into the culture medium. Furthermore, it was found that secretion of adrenomedullin is regulated by angiotensin II and forskolin. Studies on the actions of adrenomedullin and calcitonin gene-related peptide (CGRP) revealed a stimulatory effect of adrenomedullin, but not of CGRP, on aldosterone and cortisol secretion. These data suggest that adrenomedullin is not acting by a CGRP receptor-mediated mechanism in the H295R cell line. Adrenomedullin was also found to increase cAMP production, suggesting that in the adrenal, as in other cell types, cAMP is a second messenger for adrenomedullin action. However, the effects of adrenomedullin were not fully mimicked by forskolin, possibly suggesting a role for an additional second messenger. The presence of mRNA encoding both the putative adrenomedullin receptors, L1 and calcitonin receptorlike receptor/receptor-associated modulatory protein 2 (CRLR/RAMP-2), was demonstrated in H295R cells, but RAMP-1 was not detected, suggesting that these cells do not express the CGRPI receptor CRLR/RAMP-1. Taken together, these data have demonstrated that adrenomedullin is synthesised and secreted by H295R cells. The observed rate of adrenomedullin synthesis suggests that this peptide exerts a paracrine/autocrine effect in this adrenocortical cell line, probably acting through a specific adrenomedullin receptor, to stimulate steroidogenesis and increase aldosterone synthase expression.

Comparison of Ca2+ currents of peptidergic neurons developing differing morphology with time in culture.

1997 ◽  
Vol 200 (4) ◽  
pp. 723-733
Author(s):  
D E Meyers ◽  
I M Cooke
Keyword(s):  
Defined Medium ◽  
Small Cells ◽  
Neurosecretory System ◽  
Patch Clamp Technique ◽  
Whole Cell Patch Clamp ◽  
Current Voltage ◽  
Mature Neurons ◽  
Average Current ◽  
Culturing Conditions ◽  
Ca2 Channels

The whole-cell patch-clamp technique was used to examine Ca2+ currents (ICa) in mature neurons cultured in defined medium and derived from the principal neurosecretory system of decapod crustaceans, the X-organ-sinus gland. After 1 day in culture, X-organ neurons of the crab Cardisoma carnifex showed vigorous outgrowth characterized either by the production of broad lamellipodia (veils) or, from smaller somata, a branching morphology. The neurons developing veils (veilers) had a large ICa (approximately 650 pA) and ICa current density (approximately 5 microA cm-2) while other types of neuron had little or no ICa. This distinction between the two types was still present after 5-6 days in culture. However, morphologies observed after additional outgrowth, when correlated with the ICa responses, allowed four groups to be distinguished: (1) veilers and (2) branching veilers, which developed from veilers and had a similar ICa density (approximately 3 microA cm-2); and, developing from the 1 day branchers, (3) spiny branchers or (4) small cells (ICa density approximately 0.8 microA cm-2). Immunoreactivity indicative of the presence of crustacean hyperglycemic hormone was found in all veilers and branching veilers tested, while moltinhibiting hormone reactivity, when observed, was seen in cells having a robust ICa density (> or = 1.2 microA cm-2). Normalized average current-voltage curves for each morphological group were examined for changes with increasing time in culture. The curves were consistent with the ICa being produced by a population of high-voltage-activated Ca2+ channels whose properties are biophysically indistinguishable and unaffected by time in culture. The averaged peak current did not change, despite an increase in neuronal surface area as outgrowth proceeded, and this resulted in a reduction of ICa density. This indicated that net addition of Ca2+ channels did not match the addition of new membrane under our culturing conditions.

Activation of metabotropic glutamate receptors decreases a high-threshold calcium current in spiking neurons of the Xenopus retina

1996 ◽  
Vol 13 (3) ◽  
pp. 549-557 ◽  
Author(s):  
Abram Akopian ◽  
Paul Witkovsky
Keyword(s):  
G Protein ◽  
Calcium Current ◽  
Inhibitory Effect ◽  
Spiking Neurons ◽  
Calcium Currents ◽  
High Threshold ◽  
Minor Effect ◽  
Patch Clamp Technique ◽  
Metabotropic Glutamate ◽  
Patch Pipette

AbstractTwo types of spiking neuron were identified among acutely dissociated neurons from the Xenopus retina by their responses to a depolarizing current step: single spikers and multiple spikers. In culture, multiple spikers had perikaryal diameters >15 μm, whereas single spikers had smaller somata, 5—10 μm in diameter. Using a conventional whole-cell patch-clamp technique, both T- and L-type calcium currents were identified in multiply spiking cells whereas only an L-type current was present in singly spiking cells. The metabotropic glutamate receptor (mGluR) agonist trans-(1S-3R)-1-amino-1,3-cyclopentane-dicarboxylic acid (trans-ACPD) significantly decreased the L-type calcium current by 46 ± 3% (mean ± S.E.M.) in both types of cell but had only a minor effect on the T-type current in multiply spiking neurons. In the presence of 50 μm 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), 100 μM quisqualate (a potent mGluR1/5 agonist) decreased the L-type calcium current by 47 ± 9% but had no effect on the T-type current. The selective mGluR4/6/7 agonist (±) 2-amino-4-phosphonobutyric acid (L-AP4, 100 μM), and the mGluR2/3 agonist (2S,3S,4S)-α-(carboxycyclopropyl)glycine (L-CCG1, 100μM) decreased the L-type calcium current by 12 ± 3% and 14 ± 2%, respectively. The inhibition of calcium current by trans-ACPD was reduced when the patch pipette contained the G-protein inhibitor, GDPβS. The presence of the G-protein activator GTPγS in the patch pipette irreversibly reduced the L-type calcium current, but was without effect on the T-type current. Heparin applied intracellularly significantly reduced the inhibitory effect of quisqualate, indicating an involvement of the inositol triphosphate (IP3) pathway in the mGluR-induced reduction of calcium current. Replacement of internal EGTA with BAPTA significantly reduced the inhibitory effect of quisqualate. In contrast, internal application of cAMP did not prevent an inhibition of calcium current by quisqualate. Thus, the mechanism by which calcium current is inhibited by mGluR seems not to involve an intracellular cAMP cascade. Our findings indicate that activation of mGluR1/5 results in the inhibition of a high-threshold calcium current. This process is mediated by the activation of a G-protein and is consistent with inhibition occurring by an lPrstimulated release of internal calcium.

Endothelial cell nitric oxide inhibits aldosterone synthesis in zona glomerulosa cells: modulation by oxygen

2000 ◽  
Vol 279 (4) ◽  
pp. E846-E854 ◽  
Author(s):  
Craig J. Hanke ◽  
William B. Campbell
Keyword(s):  
Nitric Oxide ◽  
Cultured Cells ◽  
Inhibitory Effect ◽  
Zona Glomerulosa ◽  
Ang Ii ◽  
Low Oxygen ◽  
Endogenous Nitric Oxide ◽  
Glomerulosa Cells ◽  
Deta Nonoate ◽  
Zona Glomerulosa Cells

The regulation of aldosterone synthesis by endogenous nitric oxide (NO) was examined in cultured cells of the adrenal cortex. Endothelial NO synthase (eNOS) was detected by Western blot in cultured adrenal endothelial cells (ECs) but not in zona glomerulosa (ZG) cells or adrenal fibroblasts. Neither inducible (iNOS) nor neuronal NOS (nNOS) isoforms were detected in the cells. Only ECs had NOS activity and converted [3H]l-arginine to [3H]l-citrulline. Angiotensin II (ANG II, 100 nM) increased EC production of nitrate/nitrite by 2.4-fold. Coincubation with ECs or treatment with DETA nonoate increased the fluorescence of ZG cells loaded with an NO-sensitive dye, diaminofluorescein 2 diacetate (DAF-2 DA). DETA nonoate inhibited ANG II (1 nM) and potassium (10 mM) -stimulated aldosterone release in a concentration-related manner. This inhibitory effect of NO was enhanced >10-fold by decreasing the oxygen concentration from 21 to 8%. Coincubation of EC and ZG cells in 8% oxygen inhibited ANG II-induced aldosterone release, and inhibition was reversed by blockade of NOS. These findings indicate that adrenal EC-derived NO inhibits aldosterone release by cultured ZG cells and that the sensitivity to NO inhibition is increased at low oxygen concentrations.

Characteristics of two types of calcium channels in rat pituitary gonadotrophs

1989 ◽  
Vol 257 (5) ◽  
pp. C865-C874 ◽  
Author(s):  
A. Stutzin ◽  
S. S. Stojilkovic ◽  
K. J. Catt ◽  
E. Rojas
Keyword(s):  
Low Frequency ◽  
Cell Types ◽  
Fold Change ◽  
Inactivation Kinetics ◽  
Patch Clamp Technique ◽  
Activation Curve ◽  
Transient Component ◽  
Rat Pituitary ◽  
Voltage Dependent ◽  
Ca2 Channels

The properties of Ca2+ channels in cultured rat pituitary gonadotrophs were analyzed by the patch-clamp technique. The inward Ca2+ currents, recorded in the presence of 5.2 mM Ca2+ or Ba2+, included a fast, transient component with activation-inactivation kinetics and a delayed component with slower activation. The midpoint of the activation curve lay at -30 mV for the transient component and at -12 mV for the delayed component. At the midpoint, changes in potential of 9.5 and 13 mV induced an e-fold change in the activation of the transient and delayed components, respectively. The rate of inactivation of the first component was strongly voltage dependent. At -43 mV, a 7.4-mV change in potential induced an e-fold change in the fraction of Ca2+ channels available to conduct Ca2+ current. During long-lasting (100-200 ms) low-frequency depolarizing voltage-clamp pulses, the size of the delayed component of the Ca2+ current remained constant. The differential effects of membrane potential on inactivation and the different time constants for activation of the two components of the Ca2+ conductance indicate the presence of two types of Ca2+ channels in the membrane of the gonadotroph: the rapidly inactivating current appears to be attributable to a T-type channel, and the noninactivating current corresponds to the L-type channel described in many other cell types.

Comparison of lactotrope subtypes of neonatal and adult male rats: plaque assays and patch-clamp studies

1993 ◽  
Vol 265 (1) ◽  
pp. E121-E127 ◽  
Author(s):  
R. Felix ◽  
J. Horta ◽  
G. Cota
Keyword(s):  
Patch Clamp ◽  
Adult Male ◽  
Plaque Assay ◽  
Male Rats ◽  
High Threshold ◽  
Pituitary Cells ◽  
Patch Clamp Technique ◽  
Large Plaque ◽  
And Function ◽  
Ca2 Channels

We examined the differences in lactotrope number and function between pituitary cultures from neonatal (10-day-old) and adult male rats. Basal hormone release was measured with the reverse hemolytic plaque assay. Whole cell Ba2+ currents through Ca2+ channels were recorded from identified prolactin (PRL) secretors with the patch-clamp technique. Lactotropes were classified in two groups according to the relative amount of PRL released: small-plaque (SP) secretors accounted for 6% of all cells in both neonatal and adult pituitary cultures, whereas large-plaque (LP) secretors comprised 13% of the adult pituitary cells but were scarce in cultures from neonates. Simultaneous plaque assays for PRL and growth hormone (GH) showed that in adults as well as in neonates the number of SP and LP secretors was similar to the number of lactosomatotropes (PRL cells that also release GH) and classical lactotropes (PRL-only cells), respectively. Ba2+ current density at positive membrane potentials was markedly higher in adult LP secretors than in neonatal or adult SP lactotropes. We conclude that the appearance of LP secretors constitutes a major postnatal change within the rat lactotrope population. These cells present a large activity of high-threshold Ca2+ channels in the plasma membrane, release PRL at high basal rates, and may correspond to classical lactotropes. The results further suggest that neonatal lactotrope-like cells persist during development and give place to adult SP secretors.

scholarly journals Study and Assessment of Defect and Trap Effects on the Current Capabilities of a 4H-SiC-Based Power MOSFET

Electronics ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 735
Author(s):  
Fortunato Pezzimenti ◽  
Hichem Bencherif ◽  
Giuseppe De Martino ◽  
Lakhdar Dehimi ◽  
Riccardo Carotenuto ◽  
...  
Keyword(s):  
Drain Current ◽  
Oxide Semiconductor ◽  
Temperature Dependent ◽  
Channel Mobility ◽  
Blocking Voltage ◽  
Current Voltage ◽  
Wide Range ◽  
Temperature Ranges ◽  
Joint Contribution ◽  
State Resistance

A numerical simulation study accounting for trap and defect effects on the current-voltage characteristics of a 4H-SiC-based power metal-oxide-semiconductor field effect transistor (MOSFET) is performed in a wide range of temperatures and bias conditions. In particular, the most penalizing native defects in the starting substrate (i.e., EH6/7 and Z1/2) as well as the fixed oxide trap concentration and the density of states (DoS) at the 4H-SiC/SiO2 interface are carefully taken into account. The temperature-dependent physics of the interface traps are considered in detail. Scattering phenomena related to the joint contribution of defects and traps shift the MOSFET threshold voltage, reduce the channel mobility, and penalize the device current capabilities. However, while the MOSFET on-state resistance (RON) tends to increase with scattering centers, the sensitivity of the drain current to the temperature decreases especially when the device is operating at a high gate voltage (VGS). Assuming the temperature ranges from 300 K to 573 K, RON is about 2.5 MΩ·µm2 for VGS > 16 V with a percentage variation ΔRON lower than 20%. The device is rated to perform a blocking voltage of 650 V.

scholarly journals Amphetamine-Decreased Progesterone and Estradiol Release in Rat Granulosa Cells: The Regulatory Role of cAMP- and Ca2+-Mediated Signaling Pathways

Biomedicines ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 493
Author(s):  
 Chung-Yu Chen ◽  
Chien-Rung Chen ◽  
Chiao-Nan Chen ◽  
Paulus S. Wang ◽  
Toby Mündel ◽  
...  
Keyword(s):  
Granulosa Cells ◽  
Prostaglandin F2α ◽  
Inhibitory Effect ◽  
Inhibitory Effects ◽  
Steroidogenic Enzyme ◽  
Estradiol Secretion ◽  
Basal Release ◽  
Ca2 Channels

The purpose of this study is to evaluate the amphetamine effects on progesterone and estradiol production in rat granulosa cells and the underlying cellular regulatory mechanisms. Freshly dispersed rat granulosa cells were cultured with various test drugs in the presence of amphetamine, and the estradiol/progesterone production and the cytosolic cAMP level were measured. Additionally, the cytosolic-free Ca2+ concentrations ([Ca2+]i) were measured to examine the role of Ca2+ influx in the presence of amphetamine. Amphetamine in vitro inhibited both basal and porcine follicle-stimulating hormone-stimulated estradiol/progesterone release, and amphetamine significantly decreased steroidogenic enzyme activities. Adding 8-Bromo-cAMP did not recover the inhibitory effects of amphetamine on progesterone and estradiol release. H89 significantly decreased progesterone and estradiol basal release but failed to enhance a further amphetamine inhibitory effect. Amphetamine was capable of further suppressing the release of estradiol release under the presence of nifedipine. Pretreatment with the amphetamine for 2 h decreased the basal [Ca2+]i and prostaglandin F2α-stimulated increase of [Ca2+]i. Amphetamine inhibits progesterone and estradiol secretion in rat granulosa cells through a mechanism involving decreased PKA-downstream steroidogenic enzyme activity and L-type Ca2+ channels. Our current findings show that it is necessary to study the possibility of amphetamine perturbing reproduction in females.

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