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Effects of barium ions on the resting membrane potential of frog striated muscle fibres
Life Sciences Vol . 4, pp. 77-81, 1985. Pergamon Press Ltd. Printed in Cyreat Britain .
EFFECTS OF BARIDM IONS ON THE RESTING MEMBRANE POTENTIAL OF FROG STRIATED MIISCLE FIBRES M . Josse*, J .A . Cerf and G . Hulin Laboratory of Neurophyeiology, Faculty of Sciences, üaiveraity of Brussels
(Received 17 September 1984; in final form 12 November 1984) AVAILABLE data on the effects of barium on the resting potential are mostly conoerned with nerve l ' 2 ' 3 and smooth muscle fibres . 4
Ia frog
striated muscle, however, it has been reported that barium ions are unable to prevent the fall in resting potential resulting from calcium depletion . 5 This preliminary report deals with the action of bariua on the resting meabrane potential of frog skeletal muscle fibres, and its dependence on the ionic composition of the ezteraal medium . Methods The experiments xere performed on the eartoriue muscle of Rana temporaries .
The isolated muscle was mounted in a lucite chamber and
submitted to continuous perfusion .
The 'normal' Ringer's solution had
the following composition : NaCl 112 mM, 8HC0 3 2 mM, CaCl 2
1 .8
mM .
Potassium-rich media were prepared by substituting KC1 for equimolar amounts of NaCl in the Ringer's solution .
Sodium-deficient and chloride-
free solutions were obtained by replacing NaCl by guanidine chloride and sodiua methyleulphate respectively .
Calcium-free medin were prepared by
omitting CaC12 in the composition of the various solutions . containing media were made by adding *
1 .8
Barium-
or 5 .4 mM BaC1 2 to the above
'Aspirant' of the National Foundation for Scientific Research (F .N .R .S .) .
77
EFFECTS OF BARIUM IONS
78
Vol. 4, No . 1
FIG . 1 Influence of potassiua concentration in the Ringer's solution on the depolarizing effect of 9 .4 mM barium . Each column represents the average membrane potential of at least 10 fibres from four different muscles (A, B,C and D) submitted to a series of treatments . For each muscle, the sequence of administration of the different solutions reads from left to right ; the indicated alterations in eompoaition of the perfusion fluid are cumulative . The resting potential was measured 30 min after each change of solution . Vertical bars represent 2 x S .E .
_E
F2
W F O 6 w 2 F w
W
c
.O
ro
0
FIG . 2 Influence of sodium concentration in the calcium-free Ringer s solution Rach column represents the on the repolarizing effect of 5 .4 mM barium . average membrane potential of at least 10 fibres from four different For each muscles (A,B,C and D) submitted to a series of treatments . muscle, the sequence of administration of the different solutions reads frog left to right ; the indicated alterations is composition of the perfusion fluid are cumulative . The resting potential was measured 30 min after changing the sodium concentration, 45 min after calcium deprivation, and 10 min after addition of bariua . Vertical bars represent 2 x S .E .
EFFECTS OF BARIUM IONS
Vol . 4, No. 1 solutions .
79
The membrane potential of the mueole fibres was recorded
using conventional microelectrodes .
The resting potential of at leant
10 fibree was measured initially in normal Ringer, and in eeah one of the modified solutions used sequentially . Results I.
Effects of barium added to Ringer's solution A progressive fall is resting potential occurred when barium wan
added to the Ringer's solution, although a alight increase could be detected is some fibres during the first few minutes of treatment . rate of decline generally
decreased after
30
The
min, at which tins the
resting potential had fallen by an average of 29 .5 (* 2 .6 S .E .) or
37.7
mV (* 2 .5 S .E .) with 1 .8 or
5.4
mM barium respective]y .
It was found that when the fibree were initially depolarized by increasing the potassium coaoentration in the Ringer's solution (10 or
20
mM), the depolarization occurring oa further addition of barium wan
lessened .
Thin effect is shown in Fig . 1, which represents a typical
experiment on
4
muscles treated with different potassium concentrations
prior to the addition of
5 .4
mM barium .
In other experiments at normal potassium concentration, absence of sodium in the perfusion fluid did not prevent the depolarization produced by subeequeat addition of barium ; however, in a sodium-free guanidine Ringer's solution the fall is resting potential produced by
5 .4
mM barium was reduced by about 10 mV .
The depolarizing effect of
barium was unaltered is a chloride-free Ringer's solution . II .
Effects of barium added to calcium-free Ringer's solution Striated muscle fibree treated with a calcium-free Ringer's solu-
Lion suffer e progressive ía11 in resting potential . 6
In the present
experiments, the depolarization produced by calcium lack averaged
28 .7
mV after
45
min .
Under these calcium-free conditions, the muaclee
treated xith solutions containing
1.8
or
5.4
~M barium revealed a
80
Vol. 4, No . 1
EFFECTS OF H~ARItJM IONS
transient rise in membrane potential .
The fibres were repolarized
within 10 min by an average of 13 .5 (* 2 .8 S .S .) or 19 .4 aV (* 2.6 S .E .) with 1 .8 or 5 .4 mH barius reapeatively . Thin effect depended on the sodium concentration is the ezternal aedina .
Indeed, the transient repolarization produced by barium was
decreased when the mueale wan treated with a sodius-poor solution prior to the calcium depletion ; it gave way to an immediate depolarization when the sodium concentration had been anfficieatly lowered .
Fig . 2
represents a typical ezperimeat on 4 muaalea perfueed initially with eolutions containing various aaounts of sodium, next submitted to oaloium l~ok, cad finally treated with 5 .4 aM barlna . The magnitude of the repolar3zing effect of bariua (in presence of 112 aM aodiua) wan saintaiaed when the ezternal potaeeiua concentration wan increased from 2 to 5 m?i before withdrawal of calcium ; however, the average iaareaae in resting potential produced by 5 .4 mM barius was only
6 mV when the aaleiua-free solution contained 10 a!S potassium . Disouasion The diphasio effect of bariua oa the renting potential, i .e . a alight and transient increase followed by a progressive fall, has bees reported previously is other ezaitable tiasuee . l~
The effect of barius
on the membrane potential of striated auaals fibres can tentatively be interpreted in terms of membrane permeability changes, in keeping with the constant field equation .
Indeed, the fast that barium produces as
increase 1n aeabrane resistance $ indicates a lowered ionic permeability . The transient repolariziag effect of barius, clearlT observed in the calcium-free Ringer's aolutioa and shown to be sodium dependent, auggents an initial deoreaee is membrane permeability to this ion (PRa ) . The effect of a reduction of PNa is lean significant is presence of high ezternal potassium, as the contribution of these ions to the membrane potential largely dominates over that of sodium ions .
On
Vol . 4, No . 1
EFFECTS OF BARIUM IONS
81
the other haad, the mesbraae depolarisatioa oharaoteriaing the action of barium added to normal Ringer's solution seems easentiall~r related to a progressive decrease in permeability to potasaius ions (PK ) .
Thin aeaha-
nias xould operate principally at lox external potaesina aonoentratione, when the iraotion of the membrane potential attributable to other ions tends already to dominate the contribution of potassins ions .
Thus, it
seems that the effeota of barlus on the resting potential of striated suaole tibrea aan be ezplaiasd by a dnal action ezerted oa sembrane
Na
permeability, vis . an initial reduction of P
g
folloxed by a mark " d but
more gradual decrease in P . Aakaoxledgmeata - This xork xas aided by a graat íros the Foundation for Mediaal Saieatific Researoh (F .R .S .M .) . We are also indebtgd to the CompanT 'La Prdvoyaaae Sociale', of Brussels, for fiaaaoial support . Refersncee R . ROBER and $ . STROBE, Pflüg . Arch .
ásá, 71 (1929) .
2.
R . LORENTE de NO and T .P . FEND, J . Cell . Comp . Ph7siol .
3.
T . NARAHA$$I, J . Phyaiol .
4.
E . BIILBRINß and H . KIIRIYAMA, J . Pk~TSiol .
5.
D .J . JENDEN and J .F . REDER, J . Physiol .
ó.
% . AIIBERT, Handb . d . ezp . Pharmakol ., Erg . W .,
7.
A .L . HODGKIN and B . KATZ, J . Physiol .
8.
M . TAMASIGE, Anaot . cool .
~~6, 389 (1961) .
lap .
á=4,
á8,
397 (1946) .
166, 29 (1963) . ¢6~, 889 (1963) .
á~ ~ 1, 337 (1963) . =08, 37 (1949) .
141 (1951) .
EFFECTS OF BARIDM IONS ON THE RESTING MEMBRANE POTENTIAL OF FROG STRIATED MIISCLE FIBRES M . Josse*, J .A . Cerf and G . Hulin Laboratory of Neurophyeiology, Faculty of Sciences, üaiveraity of Brussels
(Received 17 September 1984; in final form 12 November 1984) AVAILABLE data on the effects of barium on the resting potential are mostly conoerned with nerve l ' 2 ' 3 and smooth muscle fibres . 4
Ia frog
striated muscle, however, it has been reported that barium ions are unable to prevent the fall in resting potential resulting from calcium depletion . 5 This preliminary report deals with the action of bariua on the resting meabrane potential of frog skeletal muscle fibres, and its dependence on the ionic composition of the ezteraal medium . Methods The experiments xere performed on the eartoriue muscle of Rana temporaries .
The isolated muscle was mounted in a lucite chamber and
submitted to continuous perfusion .
The 'normal' Ringer's solution had
the following composition : NaCl 112 mM, 8HC0 3 2 mM, CaCl 2
1 .8
mM .
Potassium-rich media were prepared by substituting KC1 for equimolar amounts of NaCl in the Ringer's solution .
Sodium-deficient and chloride-
free solutions were obtained by replacing NaCl by guanidine chloride and sodiua methyleulphate respectively .
Calcium-free medin were prepared by
omitting CaC12 in the composition of the various solutions . containing media were made by adding *
1 .8
Barium-
or 5 .4 mM BaC1 2 to the above
'Aspirant' of the National Foundation for Scientific Research (F .N .R .S .) .
77
EFFECTS OF BARIUM IONS
78
Vol. 4, No . 1
FIG . 1 Influence of potassiua concentration in the Ringer's solution on the depolarizing effect of 9 .4 mM barium . Each column represents the average membrane potential of at least 10 fibres from four different muscles (A, B,C and D) submitted to a series of treatments . For each muscle, the sequence of administration of the different solutions reads from left to right ; the indicated alterations in eompoaition of the perfusion fluid are cumulative . The resting potential was measured 30 min after each change of solution . Vertical bars represent 2 x S .E .
_E
F2
W F O 6 w 2 F w
W
c
.O
ro
0
FIG . 2 Influence of sodium concentration in the calcium-free Ringer s solution Rach column represents the on the repolarizing effect of 5 .4 mM barium . average membrane potential of at least 10 fibres from four different For each muscles (A,B,C and D) submitted to a series of treatments . muscle, the sequence of administration of the different solutions reads frog left to right ; the indicated alterations is composition of the perfusion fluid are cumulative . The resting potential was measured 30 min after changing the sodium concentration, 45 min after calcium deprivation, and 10 min after addition of bariua . Vertical bars represent 2 x S .E .
EFFECTS OF BARIUM IONS
Vol . 4, No. 1 solutions .
79
The membrane potential of the mueole fibres was recorded
using conventional microelectrodes .
The resting potential of at leant
10 fibree was measured initially in normal Ringer, and in eeah one of the modified solutions used sequentially . Results I.
Effects of barium added to Ringer's solution A progressive fall is resting potential occurred when barium wan
added to the Ringer's solution, although a alight increase could be detected is some fibres during the first few minutes of treatment . rate of decline generally
decreased after
30
The
min, at which tins the
resting potential had fallen by an average of 29 .5 (* 2 .6 S .E .) or
37.7
mV (* 2 .5 S .E .) with 1 .8 or
5.4
mM barium respective]y .
It was found that when the fibree were initially depolarized by increasing the potassium coaoentration in the Ringer's solution (10 or
20
mM), the depolarization occurring oa further addition of barium wan
lessened .
Thin effect is shown in Fig . 1, which represents a typical
experiment on
4
muscles treated with different potassium concentrations
prior to the addition of
5 .4
mM barium .
In other experiments at normal potassium concentration, absence of sodium in the perfusion fluid did not prevent the depolarization produced by subeequeat addition of barium ; however, in a sodium-free guanidine Ringer's solution the fall is resting potential produced by
5 .4
mM barium was reduced by about 10 mV .
The depolarizing effect of
barium was unaltered is a chloride-free Ringer's solution . II .
Effects of barium added to calcium-free Ringer's solution Striated muscle fibree treated with a calcium-free Ringer's solu-
Lion suffer e progressive ía11 in resting potential . 6
In the present
experiments, the depolarization produced by calcium lack averaged
28 .7
mV after
45
min .
Under these calcium-free conditions, the muaclee
treated xith solutions containing
1.8
or
5.4
~M barium revealed a
80
Vol. 4, No . 1
EFFECTS OF H~ARItJM IONS
transient rise in membrane potential .
The fibres were repolarized
within 10 min by an average of 13 .5 (* 2 .8 S .S .) or 19 .4 aV (* 2.6 S .E .) with 1 .8 or 5 .4 mH barius reapeatively . Thin effect depended on the sodium concentration is the ezternal aedina .
Indeed, the transient repolarization produced by barium was
decreased when the mueale wan treated with a sodius-poor solution prior to the calcium depletion ; it gave way to an immediate depolarization when the sodium concentration had been anfficieatly lowered .
Fig . 2
represents a typical ezperimeat on 4 muaalea perfueed initially with eolutions containing various aaounts of sodium, next submitted to oaloium l~ok, cad finally treated with 5 .4 aM barlna . The magnitude of the repolar3zing effect of bariua (in presence of 112 aM aodiua) wan saintaiaed when the ezternal potaeeiua concentration wan increased from 2 to 5 m?i before withdrawal of calcium ; however, the average iaareaae in resting potential produced by 5 .4 mM barius was only
6 mV when the aaleiua-free solution contained 10 a!S potassium . Disouasion The diphasio effect of bariua oa the renting potential, i .e . a alight and transient increase followed by a progressive fall, has bees reported previously is other ezaitable tiasuee . l~
The effect of barius
on the membrane potential of striated auaals fibres can tentatively be interpreted in terms of membrane permeability changes, in keeping with the constant field equation .
Indeed, the fast that barium produces as
increase 1n aeabrane resistance $ indicates a lowered ionic permeability . The transient repolariziag effect of barius, clearlT observed in the calcium-free Ringer's aolutioa and shown to be sodium dependent, auggents an initial deoreaee is membrane permeability to this ion (PRa ) . The effect of a reduction of PNa is lean significant is presence of high ezternal potassium, as the contribution of these ions to the membrane potential largely dominates over that of sodium ions .
On
Vol . 4, No . 1
EFFECTS OF BARIUM IONS
81
the other haad, the mesbraae depolarisatioa oharaoteriaing the action of barium added to normal Ringer's solution seems easentiall~r related to a progressive decrease in permeability to potasaius ions (PK ) .
Thin aeaha-
nias xould operate principally at lox external potaesina aonoentratione, when the iraotion of the membrane potential attributable to other ions tends already to dominate the contribution of potassins ions .
Thus, it
seems that the effeota of barlus on the resting potential of striated suaole tibrea aan be ezplaiasd by a dnal action ezerted oa sembrane
Na
permeability, vis . an initial reduction of P
g
folloxed by a mark " d but
more gradual decrease in P . Aakaoxledgmeata - This xork xas aided by a graat íros the Foundation for Mediaal Saieatific Researoh (F .R .S .M .) . We are also indebtgd to the CompanT 'La Prdvoyaaae Sociale', of Brussels, for fiaaaoial support . Refersncee R . ROBER and $ . STROBE, Pflüg . Arch .
ásá, 71 (1929) .
2.
R . LORENTE de NO and T .P . FEND, J . Cell . Comp . Ph7siol .
3.
T . NARAHA$$I, J . Phyaiol .
4.
E . BIILBRINß and H . KIIRIYAMA, J . Pk~TSiol .
5.
D .J . JENDEN and J .F . REDER, J . Physiol .
ó.
% . AIIBERT, Handb . d . ezp . Pharmakol ., Erg . W .,
7.
A .L . HODGKIN and B . KATZ, J . Physiol .
8.
M . TAMASIGE, Anaot . cool .
~~6, 389 (1961) .
lap .
á=4,
á8,
397 (1946) .
166, 29 (1963) . ¢6~, 889 (1963) .
á~ ~ 1, 337 (1963) . =08, 37 (1949) .
141 (1951) .