Voltage Dependence of Na-Ca Exchange in Barnacle Muscle Cells

1996 ◽  
Vol 779 (1) ◽  
pp. 236-248 ◽  
Author(s):  
H. RASGADO-FLORES ◽  
R. ESPINOSA-TANGUMA ◽  
J. TIE ◽  
J. DeSANTIAGO
Keyword(s):  
Voltage Dependence ◽  
Muscle Cells ◽  
Barnacle Muscle

External Ca effect on water permeability, regulatory volume decrease, and extracellular space in barnacle muscle cells

1993 ◽  
Vol 265 (4) ◽  
pp. C1128-C1137 ◽  
Author(s):  
D. M. Berman ◽  
C. Pena-Rasgado ◽  
M. Holmgren ◽  
P. Hawkins ◽  
H. Rasgado-Flores
Keyword(s):  
Water Permeability ◽  
Extracellular Space ◽  
Regulatory Volume Decrease ◽  
Three Dimensional ◽  
Muscle Cells ◽  
Barnacle Muscle ◽  
Dimensional Reconstruction ◽  
The Mean ◽  
The Relationship ◽  
Volume Decrease

The effect of extracellular Ca2+ (Cao) on sarcolemmal hydraulic water permeability (L'p), regulatory volume decrease (RVD), and extracellular space (ECS) was studied in barnacle muscle cells. Absence or presence of Cao had no effect on L'p [0 Cao = 2.762 +/- 0.098 x 10(-5), and 11 mM Cao = 2.720 +/- 0.222 x 10(-5) cm.kg.s-1 x osmol x 1-kgH2O-1]. Likewise, cells exposed to anisosmotic media (for < 30 min) behaved as osmometers in 0 and 11 mM Cao, showing similar slopes and intercepts in van't Hoff plots. At longer incubation times, however, hyposmotic conditions promoted a Cao-dependent RVD. The relationship between Cao and the percentage of cells responding with RVD to a hyposmotic challenge was sigmoidal (half-maximal Cao = 4.83 mM). The mean rate of RVD (40 nl/min) was independent of the level of swelling in response to hyposmotic challenges. However, the magnitude of RVD increased with larger hyposmotic challenges. Both the presence of Cao and hypotonicity reduced the "apparent" ECS by 47 +/- 6 and 39 +/- 6%, respectively. Three-dimensional reconstruction of autoradiographs of the cells was made to interpret these results.

Stoichiometry and Regulation of the Na-Ca Exchanger in Barnacle Muscle Cells

1991 ◽  
Vol 639 (1 Sodium-Calciu) ◽  
pp. 22-33 ◽  
Author(s):  
HECTOR RASGADO-FLORES ◽  
JAIME DESANTIAGO ◽  
RICARDO ESPINOSA-TANGUMA
Keyword(s):  
Muscle Cells ◽  
Barnacle Muscle

The influence of "nonmyoplasmic" sodium on the measured value of the sodium efflux from barnacle muscle

1981 ◽  
Vol 59 (12) ◽  
pp. 1219-1227 ◽  
Author(s):  
M. R. Menard ◽  
J. A. M. Hinke
Keyword(s):  
Extracellular Space ◽  
Striated Muscle ◽  
Muscle Cells ◽  
Sodium Content ◽  
Flame Photometry ◽  
Free Solution ◽  
Sodium Efflux ◽  
Barnacle Muscle ◽  
Total Sodium

In single striated muscle cells of the giant barnacle Balanus nubilus, the sodium content of the myoplasm was measured with an intracellular microelectrode, and the total sodium content of the cell was measured by flame photometry, during immersion of the cells in sodium-free solution. The sodium content of the myoplasm declined slowly but steadily from ca. 10 mmol/kg water to ca. 4 mmol/kg water during immersions lasting up to 16 h. The "nonmyoplasmic" sodium content of the cells, defined as the sodium content after subtraction of the sodium in the extracellular (sorbitol) space and in the myoplasm, declined rapidly from ca. 15 mmol/kg water to ca. 3 mmol/kg water during the first 30 min of immersion in sodium-free solution, but remained constant thereafter. The rapidly lost portion of the nonmyoplasmic sodium (ca. 12 mmol/kg water) was ascribed to the extracellular space but the location of the inexchangeable portion was not discovered. The behavior of the efflux of 22Na which was loaded into the myoplasm by microinjection was consistent with this interpretation. It was concluded that the nonmyoplasmic sodium does not have an appreciable influence on the measured value of the sodium efflux from the myoplasm of barnacle muscle cells.

scholarly journals Effect of pentachlorophenol on calcium accumulation in barnacle muscle cells.

1996 ◽  
Vol 491 (1) ◽  
pp. 13-20 ◽  
Author(s):  
J C Nwoga ◽  
J C Sniffen ◽  
C Peña-Rasgado ◽  
V A Kimler ◽  
H Rasgado-Flores
Keyword(s):  
Muscle Cells ◽  
Calcium Accumulation ◽  
Barnacle Muscle

Aminopyridine inhibition and voltage dependence of K+ currents in smooth muscle cells from cerebral arteries

1994 ◽  
Vol 267 (6) ◽  
pp. C1589-C1597 ◽  
Author(s):  
B. E. Robertson ◽  
M. T. Nelson
Keyword(s):  
Smooth Muscle ◽  
Steady State ◽  
Smooth Muscle Cells ◽  
Voltage Dependence ◽  
Muscle Cells ◽  
Membrane Depolarization ◽  
K Channels ◽  
Voltage Dependent ◽  
Basilar Arteries ◽  
K Currents

Voltage-dependent K+ currents were characterized using the patch-clamp technique in smooth muscle cells isolated from rabbit cerebral (basilar) arteries. This study focused on the voltage dependence and the pharmacology of these K+ currents, since this information will be useful for the investigation of the role of the voltage-dependent K+ channels in arterial function. Currents through Ca(2+)-activated K+ (KCa) channels were minimized by buffering intracellular Ca2+ to low levels and by blockers (tetraethylammonium and iberiotoxin) of these channels. Membrane depolarization increased K+ currents, independent of changes in the driving force for K+ movement. With 140 mM internal and external K+, activation of K+ currents by membrane depolarization was half maximal at about -10 mV and increased as much as e-fold per 11 mV. Inactivation also depended on voltage, with a midpoint at -44 mV. 3,4-Diaminopyridine (3,4-DAP),4-aminopyridine(4-AP),3-amino-pyridine(3-AP), and 2-aminopyridine (2-AP) inhibited voltage-dependent K+ currents. At 0 mV, 3,4-DAP, 4-AP, 3-AP, and 2-AP (5 mM) inhibited the K+ currents by 84, 66, 36, and 8%, respectively. Phencyclidine (100 microM) inhibited the current by 53% at 0 mV. Steady-state whole cell currents through these channels were measured at physiological membrane potentials. At -40 mV, 4-AP (5 mM) reduced the steady-state outward current by 2.5 pA. These results are consistent with the idea that voltage-dependent K+ channels are involved in the regulation of the membrane potential of arterial smooth muscle.

Effect of isosmotic removal of extracellular Na+ on cell volume and membrane potential in muscle cells

1994 ◽  
Vol 267 (3) ◽  
pp. C759-C767 ◽  
Author(s):  
C. Pena-Rasgado ◽  
J. C. Summers ◽  
K. D. McGruder ◽  
J. DeSantiago ◽  
H. Rasgado-Flores
Keyword(s):  
Membrane Potential ◽  
Membrane Permeability ◽  
Cell Volume ◽  
Muscle Cells ◽  
Membrane Depolarization ◽  
Cation Channels ◽  
Volume Loss ◽  
Barnacle Muscle ◽  
Nonselective Cation Channels

Isosmotic removal of extracellular Na+ (Nao) is a frequently performed manipulation. With the use of isolated voltage-clamped barnacle muscle cells, the effect of this manipulation on isosmotic cell volume was studied. Replacement of Nao by tris(hydroxymethyl)aminomethane produced membrane depolarization (approximately 20 mV) and cell volume loss (approximately 14%). The membrane depolarization was verapamil insensitive but depended on extracellular Ca2+ (Cao) and was probably due to activation of intracellular Ca2+ (Cai)-dependent nonselective cation channels. The cell volume loss did not require membrane depolarization but depended on Cao. This was probably due to an increase in Cai, mediated by activation of Ca2+ influx via Na+/Ca2+ exchange. Nao replacement by Li+ also promoted membrane depolarization (approximately 20 mV) and cell volume loss (20%). Both effects were reduced (approximately 73%) but were not abolished by Cao removal. Under this condition, the remaining membrane depolarization was probably due to a higher membrane permeability of Li+ over Na+. The remaining cell volume loss was due to membrane depolarization, which probably induced Ca2+ release from intracellular stores.

Alpha-chymotrypsin deregulation of the sodium-calcium exchanger in barnacle muscle cells

1993 ◽  
Vol 265 (4) ◽  
pp. C1118-C1127 ◽  
Author(s):  
R. Espinosa-Tanguma ◽  
J. DeSantiago ◽  
H. Rasgado-Flores
Keyword(s):  
Muscle Cells ◽  
Monovalent Cations ◽  
Sodium Calcium Exchanger ◽  
Perfusion Rate ◽  
Dependent Effect ◽  
Barnacle Muscle ◽  
Sodium Calcium ◽  
Maximal Activation ◽  
Insight Into

To gain insight into the mechanism by which the protease alpha-chymotrypsin (alpha-chym) activates the Na-Ca exchanger in muscle cells we studied 1) the ability of this enzyme to remove the intracellular "catalytic" Ca2+ requirement for activation of all the modes of exchange mediated by the Na-Ca exchanger (i.e., Nao-Cai, Nai-Cao, Nao-Nai, and Cao-Cai, where the subscripts o and i represent extracellular and intracellular, respectively), and 2) the ability of certain monovalent cations to stimulate Cao-Cai exchange after activation of the exchanger by alpha-chym. Barnacle muscle cells were used as models because these cells are so large that they can be internally perfused and voltage clamped. The results show that alpha-chym produces a highly activated Na-Ca exchanger able to operate in all its modes of exchange independently of catalytic Cai. The concentration-dependent effect of alpha-chym was biphasic; maximal activation occurred at 0.5 mg alpha-chym/ml perfusate for 20 min of perfusion at a perfusion rate of 2.5 microliters/min. The results are discussed in terms of the possible effects of alpha-chym on the kinetic modulation of the exchanger.

Na/Ca exchange in barnacle muscle cells has a stoichiometry of 3 Na+/1 Ca2+

1987 ◽  
Vol 252 (5) ◽  
pp. C499-C504 ◽  
Author(s):  
H. Rasgado-Flores ◽  
M. P. Blaustein
Keyword(s):  
Plasma Membrane ◽  
Cell Activity ◽  
Maximum Velocity ◽  
Muscle Cells ◽  
Resting Cells ◽  
Exchange System ◽  
Ca Pump ◽  
Barnacle Muscle ◽  
Na Efflux ◽  
Lower Capacity

The portions of the 45Ca influx and 22Na efflux that were activated by physiological concentrations of intracellular free Ca2+, [Ca2+]i, were studied in internally perfused single giant barnacle muscle cells. Since both fluxes were activated by intracellular Ca2+ (Cai) and the Ca influx was dependent on internal Na+ (Nai), the fluxes appear to be coupled (Na/Ca exchange). Tracer Ca/Ca and Na/Na exchanges were eliminated by employing tris(hydroxymethyl)aminomethane (Tris) as the predominant external cation. Under these circumstances, the ratio of the external Ca2+ (Cao)-dependent, Cai-activated Na+ efflux to the Nai-dependent, Cai-activated Ca influx was 3.1-3.2 Na+/1 Ca2+, when the intracellular Na+ concentration, [Na+]i was either 30 or 46 mM. This is the first direct measurement of the Na/Ca exchange stoichiometry. In many types of cells, the Na/Ca exchange system appears to operate in parallel with a plasma membrane ATP-driven Ca pump that has a lower capacity (maximum velocity), but higher affinity for Ca2+ than the Na/Ca exchanger. The data on the stoichiometry and activation by internal Ca2+ imply that the turnover of the Na/Ca exchanger is modulated during periods of cell activity. When the cells are depolarized, the Na/Ca exchange system is activated by the rising [Ca2+]i, and Ca2+ entry via the exchanger is promoted. Then, at repolarization, Ca2+ exits rapidly, primarily via the exchanger. However, in resting cells, with a low [Ca2+]i, much (but not all) of the Ca2+ efflux is probably mediated by the ATP-driven Ca pump.

scholarly journals Kinetics and stoichiometry of coupled Na efflux and Ca influx (Na/Ca exchange) in barnacle muscle cells.

1989 ◽  
Vol 93 (6) ◽  
pp. 1219-1241 ◽  
Author(s):  
H Rasgado-Flores ◽  
E M Santiago ◽  
M P Blaustein
Keyword(s):  
Sea Water ◽  
Muscle Cells ◽  
Resting Cells ◽  
Coupling Ratio ◽  
Barnacle Muscle ◽  
Maximal Activation ◽  
Na Efflux ◽  
Kinetics Of ◽  
Mitochondrial Uncoupler ◽  
Low Rate

Coupled Na+ exit/Ca2+ entry (Na/Ca exchange operating in the Ca2+ influx mode) was studied in giant barnacle muscle cells by measuring 22Na+ efflux and 45Ca2+ influx in internally perfused, ATP-fueled cells in which the Na+ pump was poisoned by 0.1 mM ouabain. Internal free Ca2+, [Ca2+]i, was controlled with a Ca-EGTA buffering system containing 8 mM EGTA and varying amounts of Ca2+. Ca2+ sequestration in internal stores was inhibited with caffeine and a mitochondrial uncoupler (FCCP). To maximize conditions for Ca2+ influx mode Na/Ca exchange, and to eliminate tracer Na/Na exchange, all of the external Na+ in the standard Na+ sea water (NaSW) was replaced by Tris or Li+ (Tris-SW or LiSW, respectively). In both Na-free solutions an external Ca2+ (Cao)-dependent Na+ efflux was observed when [Ca2+]i was increased above 10(-8) M; this efflux was half-maximally activated by [Ca2+]i = 0.3 microM (LiSW) to 0.7 microM (Tris-SW). The Cao-dependent Na+ efflux was half-maximally activated by [Ca2+]o = 2.0 mM in LiSW and 7.2 mM in Tris-SW; at saturating [Ca2+]o, [Ca2+]i, and [Na+]i the maximal (calculated) Cao-dependent Na+ efflux was approximately 75 pmol#cm2.s. This efflux was inhibited by external Na+ and La3+ with IC50's of approximately 125 and 0.4 mM, respectively. A Nai-dependent Ca2+ influx was also observed in Tris-SW. This Ca2+ influx also required [Ca2+]i greater than 10(-8) M. Internal Ca2+ activated a Nai-independent Ca2+ influx from LiSW (tracer Ca/Ca exchange), but in Tris-SW virtually all of the Cai-activated Ca2+ influx was Nai-dependent (Na/Ca exchange). Half-maximal activation was observed with [Na+]i = 30 mM. The fact that internal Ca2+ activates both a Cao-dependent Na+ efflux and a Nai-dependent Ca2+ influx in Tris-SW implies that these two fluxes are coupled; the activating (intracellular) Ca2+ does not appear to be transported by the exchanger. The maximal (calculated) Nai-dependent Ca2+ influx was -25 pmol/cm2.s. At various [Na+]i between 6 and 106 mM, the ratio of the Cao-dependent Na+ efflux to the Nai-dependent Ca2+ influx was 2.8-3.2:1 (mean = 3.1:1); this directly demonstrates that the stoichiometry (coupling ratio) of the Na/Ca exchange is 3:1. These observations on the coupling ratio and kinetics of the Na/Ca exchanger imply that in resting cells the exchanger turns over at a low rate because of the low [Ca2+]i; much of the Ca2+ extrusion at rest (approximately 1 pmol/cm2.s) is thus mediated by an ATP-driven Ca2+ pump.(ABSTRACT TRUNCATED AT 400 WORDS)

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