scholarly journals Effects of extracellular calcium and potassium on the sodium pump of rat adrenal glomerulosa cells

2001 ◽  
Vol 280 (1) ◽  
pp. C119-C125 ◽  
Author(s):  
Douglas R. Yingst ◽  
Joanne Davis ◽  
Rick Schiebinger
Keyword(s):  
Sodium Pump ◽  
Calcium Influx ◽  
Calcium Ionophore ◽  
Extracellular Calcium ◽  
Intracellular Free Calcium ◽  
Free Calcium ◽  
Extracellular Potassium ◽  
A 23187 ◽  
Pump Activity ◽  
Glomerulosa Cells

Because the activity of the sodium pump (Na-K-ATPase) influences the secretion of aldosterone, we determined how extracellular potassium (Ko) and calcium affect sodium pump activity in rat adrenal glomerulosa cells. Sodium pump activity was measured as ouabain-sensitive 86Rb uptake in freshly dispersed cells containing 20 mM sodium as measured with sodium-binding benzofluran isophthalate. Increasing Ko from 4 to 10 mM in the presence of 1.8 mM extracellular calcium (Cao) stimulated sodium pump activity up to 165% and increased intracellular free calcium as measured with fura 2. Increasing Ko from 4 to 10 mM in the absence of Cao stimulated the sodium pump ∼30% and did not increase intracellular free calcium concentration ([Ca2+]i). In some experiments, addition of 1.8 mM Cao in the presence of 4 mM Ko increased [Ca2+]i above the levels observed in the absence of Cao and stimulated the sodium pump up to 100%. Ca-dependent stimulation of the sodium pump by Ko and Cao was inhibited by isradipine (10 μM), a blocker of L- and T-type calcium channels, by compound 48/80 (40 μg/ml) and calmidizolium (10 μM), which inhibits calmodulin (CaM), and by KN-62 (10 μM), which blocks some forms of Ca/CaM kinase II (CaMKII). Staurosporine (1 μM), which effectively blocks most forms of protein kinase C, had no effect. In the presence of A-23187, a calcium ionophore, the addition of 0.1 mM Cao increased [Ca2+]i to the level observed in the presence of 10 mM Ko and 1.8 mM Cao and stimulated the sodium pump 100%. Ca-dependent stimulation by A-23187 and 0.1 mM Cao was not reduced by isradipine but was blocked by KN-62. Thus, under the conditions that Ko stimulates aldosterone secretion, it stimulates the sodium pump by two mechanisms: direct binding to the pump and by increasing calcium influx, which is dependent on Cao. The resulting increase in [Ca2+]i may stimulate the sodium pump by activating CaM and/or CaMKII.

Effect of osmolality on cytosolic free calcium and aldosterone secretion

1992 ◽  
Vol 262 (1) ◽  
pp. E68-E75 ◽  
Author(s):  
W. Wang ◽  
N. Hayama ◽  
T. V. Robinson ◽  
R. E. Kramer ◽  
E. G. Schneider
Keyword(s):  
Calcium Influx ◽  
Potassium Concentration ◽  
Sodium Concentration ◽  
Cytosolic Calcium ◽  
Extracellular Calcium ◽  
Free Calcium ◽  
Aldosterone Secretion ◽  
Voltage Dependent ◽  
Glomerulosa Cells ◽  
Dose Dependent

Alterations in extracellular osmolality have powerful inverse effects on basal and potassium- and angiotensin-stimulated aldosterone secretion. With the use of bovine glomerulosa cells grown in primary culture, the effects of alterations in osmolality on cytosolic calcium concentration ([Ca2+]c), efflux and uptake of 45Ca2+, and aldosterone secretion were determined. Alterations in osmolality, independent of sodium concentration, have inverse effects on aldosterone secretion, which are correlated with simultaneous changes in [Ca2+]c measured using fura-2. Reductions in osmolality cause dose-dependent biphasic increases in [Ca2+]c different from the monophasic increases in [Ca2+]c produced by increases in potassium concentration. Like potassium- and angiotensin-stimulated increases in [Ca2+]c, hypotonically induced increases in [Ca2+]c are associated with an increase in 45Ca2+ efflux. Reductions in osmolality also increased the uptake of 45Ca2+, an effect apparent at 2 min and persistent for at least 30 min. In the absence of extracellular calcium, reductions in osmolality, as increases in potassium concentration but not angiotensin, fail to increase [Ca2+]c, efflux of 45Ca2+, or aldosterone secretion. In conclusion, osmolality-induced alterations in aldosterone secretion are associated with parallel changes in [Ca2+]c, effects caused by alteration in the influx of extracellular calcium. On the basis of these and previous studies, we hypothesize that osmolality affects calcium influx by activating voltage-dependent or stretch-activated calcium channels.

scholarly journals Is a rise in intracellular concentration of free calcium necessary or sufficient for stimulated cytoskeletal-associated actin?

1986 ◽  
Vol 102 (4) ◽  
pp. 1459-1463 ◽  
Author(s):  
R I Sha'afi ◽  
J Shefcyk ◽  
R Yassin ◽  
T F Molski ◽  
M Volpi ◽  
...  
Keyword(s):  
Intracellular Calcium ◽  
Pertussis Toxin ◽  
Incubation Medium ◽  
Calcium Ionophore ◽  
Calcium Ionophore A23187 ◽  
Extracellular Calcium ◽  
Intracellular Concentration ◽  
The Other ◽  
Free Calcium ◽  
Ionophore A23187

The addition of the calcium ionophore A23187 to rabbit neutrophils increases the amount of actin associated with the cytoskeleton regardless of the presence or absence of calcium in the incubation medium. In the presence of extracellular calcium, the effect of A23187 is biphasic with respect to concentration. The action of the ionophore is rapid, transient, and is inhibited by pertussis toxin, hyperosmolarity, and quinacrine. On the other hand, the addition of pertussis toxin or hyperosmolarity has small if any, effect on the rise in intracellular calcium produced by A23187. While quinacrine does not affect the fMet-Leu-Phe-induced increase in cytoskeletal actin and the polyphosphoinositide turnover, its addition inhibits completely the stimulated increase in Ca-influx produced by the same stimulus. The results presented here suggest that a rise in the intracellular concentration of free calcium is neither necessary nor sufficient for the stimulated increase in cytoskeletal-associated actin. A possible relationship between the lipid remodeling stimulated by chemoattractants and the increased cytoskeletal actin is discussed.

The relationship between secretion and intracellular free calcium in bovine adrenal chromaffin cells

1984 ◽  
Vol 4 (7) ◽  
pp. 605-611 ◽  
Author(s):  
Robert D. Burgoyne
Keyword(s):  
Chromaffin Cells ◽  
Calcium Ionophore ◽  
Calcium Ionophore A23187 ◽  
Catecholamine Release ◽  
Intracellular Free Calcium ◽  
Free Calcium ◽  
Ionophore A23187 ◽  
Adrenal Chromaffin Cells ◽  
Adrenal Chromaffin ◽  
The Relationship

The effect of carbamylcholine and the calcium ionophore A23187 on catecholamine release and intracellular free calcium, [Ca2+]i, in bovine adrenal chromaffin cells was determined. At 10−4M carbamylcholine maximal release occurred with an accompanying increase in [Ca2+]i from a basal level of 168 nM to less than 300 nM. An increase in [Ca2+]i of a similar magnitude was found following challenge with 40 nM A23187. However, in this case, no catecholamine release occurred. These results suggest that stimulation of secretion from chromaffin cells by carbamylcholine may involve additional triggers which stimulate secretion at low [Ca2+]i.

66 Orai1 IS REQUIRED TO MAINTAIN CALCIUM OSCILLATION AT FERTILIZATION IN PORCINE OOCYTES

2012 ◽  
Vol 24 (1) ◽  
pp. 145
Author(s):  
C. Wang ◽  
K. Lee
Keyword(s):  
Plasma Membrane ◽  
Embryo Development ◽  
Calcium Concentration ◽  
Calcium Influx ◽  
Calcium Entry ◽  
Intracellular Free Calcium ◽  
Calcium Oscillation ◽  
Free Calcium ◽  
Intracellular Free Calcium Concentration ◽  
Free Calcium Concentration

During mammalian fertilization, the sperm induces an oscillation in the oocyte's intracellular free calcium concentration that stimulates oocyte activation. The train of calcium spikes is maintained by an influx of calcium across the plasma membrane, probably through a mechanism known as store-operated calcium entry. Despite their importance, little is known about the identity and regulation of the calcium entry channels that mediate calcium influx at fertilization. Previously we have shown that the Orai1 protein is localised in the plasma membrane of pig oocytes and plays an important role in calcium entry after depletion of the intracellular calcium stores. In this study, we investigated the function of Orai1 in signal transduction during fertilization. In Experiment 1, Orai1 levels were down-regulated by injecting immature pig oocytes with small interfering RNA (siRNA) against Orai1; control cells were injected with scrambled siRNA. The injected oocytes were then matured in vitro for 44 h. In Experiment 2, Orai1 was overexpressed by microinjection of mRNA encoding Orai1 conjugated to the enhanced green fluorescent protein (EGFP-Orai1) 36 h after the beginning of maturation; these oocytes were incubated for an additional 8 h. At the end of the incubation period the oocytes were loaded with the calcium indicator dye fura-2 and inseminated. Changes in the intracellular free calcium concentration were monitored by means of a fluorescence imaging system. Some of the fertilized oocytes were cultured for 7 days, at which time embryo development together with the total nuclear number of the embryos were recorded. Data were subjected to 1-way ANOVA; differences between treatments were analysed using the Tukey test. The level of Orai1 protein was significantly lower in Orai1 siRNA-injected oocytes compared to the control group, as determined by Western blot, indicating successful down-regulation of Orai1. During fertilization, control oocytes displayed a series of calcium transients that lasted up to 8 h. However, in Orai1 siRNA-injected oocytes (9 out of 10 measured) only 1 calcium rise could be observed; these oocytes were unable to generate repetitive calcium signals after gamete fusion. Overexpression of Orai1 also disrupted the pattern of the normal fertilization calcium signal; the oscillation ceased after just a few Ca2+ rises in 8 out of 10 oocytes. The percentage of cleaved oocytes was lower in the siRNA-injected group compared to both non-injected or control siRNA-injected oocytes (38.4 ± 4.6% vs 70.5 ± 2.8% and 70.4 ± 2.4%; P < 0.05). The frequency of blastocyst (1.9 ± 0.8% vs11.0 ± 3.1% and 9.9 ± 1.4%) and the total cell number per blastocyst (19.8 ± 0.8 vs 36.2 ± 0.7 and 33.5 ± 5.5) was also significantly lower in oocytes with down-regulated Orai1 levels. These results indicate that an Orai1-mediated calcium influx is required to maintain proper calcium oscillation at fertilization and is also essential to support subsequent embryo development.

scholarly journals Intracellular calcium release is more efficient than calcium influx in stimulating mitochondrial NAD(P)H formation in adrenal glomerulosa cells

1997 ◽  
Vol 328 (2) ◽  
pp. 525-528 ◽  
Author(s):  
Tibor ROHÁCS ◽  
Kálmán TORY ◽  
András DOBOS ◽  
András SPÄT
Keyword(s):  
Calcium Ion ◽  
Calcium Release ◽  
Calcium Influx ◽  
Biological Significance ◽  
Ion Concentration ◽  
Free Calcium ◽  
Mitochondrial Matrix ◽  
Free Medium ◽  
Glomerulosa Cells ◽  
Calcium Ion Concentration

We compared the effect on mitochondrial NAD(P)H formation of calcium release from intracellular stores with that of calcium influx from the extracellular space. Simultaneous measurements of cytoplasmic free calcium ion concentration and mitochondrial NAD(P)H were performed on fura-PE3-loaded single rat adrenal glomerulosa cells. The effects of equipotent stimuli in terms of the evoked Ca2+ response were compared. Angiotensin II (AII; 1 nM) induced a higher amplitude NAD(P)H response than K+ (5.6-7.6 mM). Vasopressin (1 μM) also induced a greater initial NAD(P)H formation than K+, although the Ca2+ signal evoked by the two agonists had similar amplitude. To examine the effect of Ca2+ release from internal stores we applied AII in Ca2+-free medium. We compared the effect on NAD(P)H formation of Ca2+ release with Ca2+ influx induced by K+, and with capacitative Ca2+ influx induced by AII. NAD(P)H formation in response to Ca2+ release was greater than that induced by Ca2+ influx, irrespective of whether induced by K+ or AII. Our results indicate that Ca2+, presumably released in the vicinity of mitochondria, activates mitochondrial dehydrogenases more efficiently than Ca2+ entering through the plasma membrane. These data confirm the biological significance of previous observations showing that Ca2+ released from inositol 1,4,5-trisphosphate-sensitive internal stores increases mitochondrial matrix [Ca2+] to a greater extent than extracellular Ca2+.

scholarly journals Rhizobium Nod factors induce increases in intracellular free calcium and extracellular calcium influxes in bean root hairs

1999 ◽  
Vol 19 (3) ◽  
pp. 347-352 ◽  
Author(s):  
Luis Cardenas ◽  
Jose A. Feijo ◽  
Joseph G. Kunkel ◽  
Federico Sanchez ◽  
Terena Holdaway-Clarke ◽  
...  
Keyword(s):  
Root Hairs ◽  
Extracellular Calcium ◽  
Intracellular Free Calcium ◽  
Free Calcium ◽  
Nod Factors ◽  
Bean Root

scholarly journals The role of calcium influx pathways in phospholipase D activation in bovine adrenal glomerulosa cells

2009 ◽  
Vol 202 (1) ◽  
pp. 77-86 ◽  
Author(s):  
Haixia Qin ◽  
Patricia Kent ◽  
Carlos M Isales ◽  
Peter M Parker ◽  
Mariya V Wilson ◽  
...  
Keyword(s):  
Phospholipase D ◽  
Calcium Influx ◽  
Cell Model ◽  
Primary Cultures ◽  
Extracellular Potassium ◽  
Voltage Dependent ◽  
H295r Cells ◽  
Glomerulosa Cells ◽  
Influx Pathways

The steroid hormone aldosterone maintains sodium homeostasis and is therefore important in the control of blood volume and pressure. Angiotensin II (AngII) and elevated extracellular potassium concentrations ([K+]e), the prime physiologic regulators of aldosterone secretion from adrenal glomerulosa cells, activate phospholipase D (PLD) in these cells. The role of Ca2+ in the activation by these agents is unknown, although nitrendipine, a voltage-dependent Ca2+ channel antagonist, does not inhibit AngII-elicited PLD activation, despite the fact that this compound blocked elevated [K+]e-stimulated PLD activity. PLD activation triggered by AngII was also unaffected by the T-type calcium channel inhibitor nickel. Nevertheless, Ca2+ influx was required for AngII-induced PLD activation in both primary cultures of bovine adrenal glomerulosa cells and a glomerulosa cell model, the NCI H295R adrenocortical carcinoma cell line. The involvement of store-operated Ca2+ (SOC) influx and Ca2+ release-activated Ca2+ (CRAC) influx pathways in PLD activation was investigated using thapsigargin, an endoplasmic reticulum Ca2+ pump inhibitor that empties the store to induce SOC influx, and the SOC inhibitor YM-58483 (BTP2), as well as a CRAC inhibitor, tyrphostin A9. In bovine glomerulosa cells, tyrphostin A9 inhibited AngII-induced PLD activation without affecting elevated [K+]e-stimulated enzyme activity. On the other hand, differences were observed between the bovine adrenal glomerulosa and H295R cells in the involvement of Ca2+ influx pathways in PLD activation, with the involvement of the SOC pathway suggested in the H295R cells. In summary, our results indicate that Ca2+ entry only through certain Ca2+ influx pathways is linked to PLD activation.

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