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Potassium dependent relaxation of slow skeletal muscle
Life Sciences Vol. 9 Part I, pp . 415-420, Printed in Great Hrita~n
1970.
Pergamon Press
POTA33ID1I DLPTsNDLNT RBLARATION OF 3IAW 3SSLETAL MD3CLTs Richard L. Irwin and Hatharine L . Oliver National Institute oß Neurological Disease and Stroke National Institutes oß Health, Bethesda, Maryland
(Received 7 November 1969; in final form 26 January 1970)
Slow-type (tonic) skeletal muscle Bibers, originally Bound is the frog, are now known to exist is the eatraocular muscles oß human beings and other mammalian species .
Slow muscle dißßers
ßrom Bast (twitch-type) muscle is that slow ßibers can be made to develop myogeaic tension by depleting them oß Ca m ions (1) . Return oß Ca ++ relaxes the slow muscle ßibers completely provided Hf is present externally .
When R+ .is leßt out oß the
Ca++ solution used to induce relaaation the muscle loses only 85~, oß the tension brought on by Ca ++ loss (2),
~cternal S+ there-
fore seems to be as iaportaat ion ßor the relaaation oß slow muscle .
Although ao ionic ßlua date are available ßrom slow
muscle, the active transport oß Na + out oß Bast muscle is is part dependent on the eateraal g+ (3, 4, 5) .
The ATPase enzyme
related to Na+ transport orients across cell membranes and the K+ oa the side oB the membranes to which Na + is transported activates the enzyme (8, 7) .
Collation oß this inßormation suggested
that relaxation oß slow skeletal ßrog muscle might depend on as active transport system, Methods and Results The slow ßibers oß rectos abdominis muscles oß ßrogs were deprived oß H+ by Blowing H+ -Brae Ringer solutions slowly past the muscles .
Aßter H+ depletion, Bor 16 hours (Fig . 1, Table I), the
415
418
RELAXATION OF SKELETAL MUSCLE
Vol . 9, No . 7
external ßluids were changed so that the new ßluids lacked not only R+ but also Ca++ .
Although little or no tension developed
during S+ depletion the withdrawal oß Ca m induced tension in the slow ßibers (Fig . 1, Table I) . +Co -Ca++ w
1
111
+K +
1
FIG. I Relaxation aßter R+ deprivation. At -Ca++ the slow ßibers oß ßro~ rectos abdomiriis muscles were made to contract by changing to Ca+ -Brae ßluids for about 20 minutes . The aerated (5~ CO2 95% 02) 5 ml baths (23° C) ßlowed continuously at 25 ml/min Relaxation was induced by returning Ca++ without R+ at (+Cad+) and then later in the presence oß Ca++ by a ßluid containing 3 mM R+ at (+R+) ; traces C, D, and B. The dißßerent tensions shown were obtained sequentially (DCAB) ßram the same muscle which had been deprived oß R+ for 16 hors at 23o C . D . First tension response aßter 16 hours without R . C . Second response aßter another 20 minutes without R+ . A . ~hird response with R+ present through-. out, B . The return oß H was delayed 50 minutes as compared to C and D and shows the incomplete relaxation when K+ ie absent . The beginning oß traces C sad D show the increased tension due to R+ depletion which occurs in some muscles but not in others . The horizontal calibration represents 5 minutes and the vertical indicates one gram oß tension . The muscles were taken ßrom ßrogs (Rang pipions) stored at 4-8° C, Contractures Bailed to occur in control sartorius muscles which contain only Bast ßibers .
The tension in slow fibers brought on
by Ca++ depletion is mgogenic since it develops in high concentrations oß tetrodotoaia (11), tubbcurarine, procaine or atropine and aßter deprivation (1) .
The same amount oß tension developed
in response to Ca++ depletion regardless oß whether K+ was
Vol. 9, No. 7
RELAXATION OF SKELETAL MUSCLE
externally present (Fig, lA) or absent (Fig, 1D, B, C),
417 without
external B+ the rate oß tension rise appeared Blower but was not aarkedly changed (Fig . 1) .
Potassiu= deprivation in Bast muscles
produces a lowered internal H+ (8, 9, 10) .
Iß this occurs in slow
ßibers then neither ezterael nor internal H+ would have any appreciable ßunction in the development oß tension during Ca++ loss . In contrast to the lack oß eßßect oß external H+ on tension induced by Ca ++ loss, the relaaation rate upon return oß Ca ++ was markedly decreased by the prior H+ depletion and continued absence oß B+ (Fig . 1),
Aßter 18 hours oß H+ depletion the average
maximal rate oß relaxation when Ca ++ was returned without H+ was 0 .17 grams/min and aßter 10 minutes oß Ca ++ was 0 .07 grams/min (làble I), TAHLB I
THE RATE OF RELAXATION OF K+ DEPRIVED SLOW STRIATED FROG MUSCLE K+
depletion (hours) 1 .5
16
Number muscle reponses
Maximal mts . Return of Ca++ (no K+) yms/min
Rate after 10 a 30 min . of Ca++ (no K+) yms/min
Maximal rats. Retum of K+ (Cam present) qms/min
_36 53
0.11 ±,01 (2.4 ± .13)
0.03± .O1 (30 min.)
0.371 .05 (1 .4 t .11)**
_10 20
0.17 ±.02 (2.6 ± .15)*
0.07 ±.Ol (10 min.)
2.50 ± .50 (1,8 1 .18)**
* Grams of tension developed before relaxation ** Grams of tension of point of K+ return when leßt with Ca ++ but without H+ ßor longer than 10 ainutes the muscles failed to relax and tensions were maintained ßor long periods (Fig, 1-B),
without R+ deprivation the same =uncles
418
RELAXATION OF SKELETAL MUSCLE
Vol. 9, No. 7
(Table I, lower) relaxed at a rate oß 0 .53 grams/min when Cam+ was returned,
When the muscles had been deprived oß H+, and Ca ++ had
been withdrawn ßor 20 minutes and then returned for 10 minutes, the subsequent return oß H+ relaxed the muscles at an average maximal rate oß 2,5 grams/min (Table I) .
This rate is 35 times as
fast as the muscle had been relaxing immediately beßore the return oß H+ (0,07 gm/min), and ßive times as fast as when Ca ++ was returned in the presence oß H+ (0,53 gm/min),
The slower relax-
ation when Cam was returned in the presence oß H+ may indicate that under these conditions Ca m re-eatrq limits the rate oß relaxation,
Muscles deprived oß H+ for only 1 .5 hours showed the
same dependency on H+ ßor relaxation as the muscles subjected to 16 hours oß deprivation (Table I) .
The slower rate oß relaxation
upon return oß H+ aßter only 1 .5 hours of H+ deprivation may have been due to less H+ depletion, the longer period oß Ca ++ return without H+, or the extended period oß Ca ++ depletion,
The experi-
nents of both groups demonstrate is two ways that the relaxation oß slow muscle depends to a great extent on the external R+ ions : (1)
lfider ionic conditions that permit complete and rapid relax-
ation is the presence oß physiological amounts oß H+ , the absence oß H+ permits only a slow and partial relaxation, (2)
When slow
muscle is maintaining tension without external H+ the return oß H* at a physiological concentration induces a . rapid and complete relaxation, Discussion Another study showed that the tension induced iß sloa .muscle by Cam deprivation depends on external monovalent cations that can penetrate the muscle membrane (11) .
When external Na + was
replaced by organic monovalent cations that were non-penetrant (Tris or 2-amino-2-methyl-1, 3 propanediol at pH 7,2) tension
Vol . 9, No. 7
RELAXATION OF SKELETAL MUSCLE
Bailed to develop due to Ca ++ lack .
419
Substituting Na + ßor the non-
penetrant canons during the Ca++ depletion led to a prompt development oß tension .
The subsequent replacement oß the Na + by
the non-penetrating canons led to a rapid relaxation (11) .
This
relaxation occurred presumably because there was no Na + to enter the muscle ßiber to maintain tension while the Na+ inside was being rapidly lost to the external ßluid .
The muscle would now
be in a state oß relaxation under Ca ++ depletion because oß no external Na + just as when Ca ++ was removed aßter substitution oß Na + by non-penetrant canons .
The experiments just mentioned
indicate that entry oß Na+ into some muscle compartment is necessary ßor the development oß tension due to Ca ++ lack .
They
further show that without external sodium available ßor entry the tension Could not be maintained .
Since tension disappears when
tb,ere is no external Na + and because the entry oß Na + is implicated in tension development it is probable that in slow muscle Na + eßßlux is necessary ßor relaxation . Because oß the Bindings stated above, the R+-deprived muscles in contractors due to Ca ++ lose can be considered to contain excess internal Na + ; its removal would appear necessary ßor relaxation .
Iß the same transport conditions prevail in slow
muscle that do in fast, i .e ., that Na + efßlua is in part dependent on external R~ then the absence oß H+ and the subsequent ßailure oß Na + to leave the slow muscle ßibers would explain the ßailure oß the slow ßibers to relax .
Since there are no muscles known
that contain only slow ßibers no information is available ßrom slow fibers as to ionic ßlvaes or contents .
Unknown ßor the same
reason is whether the Na +-R+ activated ATPase is present in slow ßiber membranes as it is in the Bast .
Providing transport ATPase
ßunctions is slow ßibers as it does in other cells, and iß ex-
420
RELAXATION OF SKELETAL MUSCLE
Vol . 9, No. 7
ternal K+ aßßects Na + transport in slow as it does is Bast muscle (3, 4, 5), then the potassium dependent relaxation described here gould be adequately eaplained by relaxation depending on enzymatic transport . St~mar y 81ow-type skeletal muscle ßibers deprived oß K+ aad made to contract by Ca++ depletion ßa11 to relax completely when Ca ++ is returned,
Return oß external K+ , known to increase Na + trans-
port in muscle and to activate transport ATPase, induces a rapid and complete relaxâtion . Reßerences 1,
R, L, IRWIN and M, M, Hein, J . Gen . Physiol . 47, 133 (1963) .
2.
R . L . IRWIN and M . M. Hein, Am . .I . Physiol . 211,1117 (1986),
3,
R, D, HEYNEB, Pros . Roy . Soc, B .
4,
P, HOROWICZ and C, J, GERBER, J . Gen. Physiol . 48, 489 (1985), s aad A, STIENHARDT, Physiol . 198, 581 R, D, HEYNES R, J.
5,
142, 359 (1954) .
(1968) . ß.
I, M . GLYNN, J. Physiol . 160, 18P (1982),
7,
R . WSITTAH, Biocäem . .I . 84, 110 (1982) .
$.
E, J, HARRIS',
9.
H, B, BTEINBACH, J . Biol . Chem . 133, 895 (1940) .
10 .
J. Physiol . 177, 355 (1965),
R, A . BJODIN and L . A . BEAUGE, J. Gea, Physiol . 52, 389 (1988) ,
11 .
R. L . IRWIN and H, L, OLIVER, Am . J. Physiol . 217, 13 (1989) .
1970.
Pergamon Press
POTA33ID1I DLPTsNDLNT RBLARATION OF 3IAW 3SSLETAL MD3CLTs Richard L. Irwin and Hatharine L . Oliver National Institute oß Neurological Disease and Stroke National Institutes oß Health, Bethesda, Maryland
(Received 7 November 1969; in final form 26 January 1970)
Slow-type (tonic) skeletal muscle Bibers, originally Bound is the frog, are now known to exist is the eatraocular muscles oß human beings and other mammalian species .
Slow muscle dißßers
ßrom Bast (twitch-type) muscle is that slow ßibers can be made to develop myogeaic tension by depleting them oß Ca m ions (1) . Return oß Ca ++ relaxes the slow muscle ßibers completely provided Hf is present externally .
When R+ .is leßt out oß the
Ca++ solution used to induce relaaation the muscle loses only 85~, oß the tension brought on by Ca ++ loss (2),
~cternal S+ there-
fore seems to be as iaportaat ion ßor the relaaation oß slow muscle .
Although ao ionic ßlua date are available ßrom slow
muscle, the active transport oß Na + out oß Bast muscle is is part dependent on the eateraal g+ (3, 4, 5) .
The ATPase enzyme
related to Na+ transport orients across cell membranes and the K+ oa the side oB the membranes to which Na + is transported activates the enzyme (8, 7) .
Collation oß this inßormation suggested
that relaxation oß slow skeletal ßrog muscle might depend on as active transport system, Methods and Results The slow ßibers oß rectos abdominis muscles oß ßrogs were deprived oß H+ by Blowing H+ -Brae Ringer solutions slowly past the muscles .
Aßter H+ depletion, Bor 16 hours (Fig . 1, Table I), the
415
418
RELAXATION OF SKELETAL MUSCLE
Vol . 9, No . 7
external ßluids were changed so that the new ßluids lacked not only R+ but also Ca++ .
Although little or no tension developed
during S+ depletion the withdrawal oß Ca m induced tension in the slow ßibers (Fig . 1, Table I) . +Co -Ca++ w
1
111
+K +
1
FIG. I Relaxation aßter R+ deprivation. At -Ca++ the slow ßibers oß ßro~ rectos abdomiriis muscles were made to contract by changing to Ca+ -Brae ßluids for about 20 minutes . The aerated (5~ CO2 95% 02) 5 ml baths (23° C) ßlowed continuously at 25 ml/min Relaxation was induced by returning Ca++ without R+ at (+Cad+) and then later in the presence oß Ca++ by a ßluid containing 3 mM R+ at (+R+) ; traces C, D, and B. The dißßerent tensions shown were obtained sequentially (DCAB) ßram the same muscle which had been deprived oß R+ for 16 hors at 23o C . D . First tension response aßter 16 hours without R . C . Second response aßter another 20 minutes without R+ . A . ~hird response with R+ present through-. out, B . The return oß H was delayed 50 minutes as compared to C and D and shows the incomplete relaxation when K+ ie absent . The beginning oß traces C sad D show the increased tension due to R+ depletion which occurs in some muscles but not in others . The horizontal calibration represents 5 minutes and the vertical indicates one gram oß tension . The muscles were taken ßrom ßrogs (Rang pipions) stored at 4-8° C, Contractures Bailed to occur in control sartorius muscles which contain only Bast ßibers .
The tension in slow fibers brought on
by Ca++ depletion is mgogenic since it develops in high concentrations oß tetrodotoaia (11), tubbcurarine, procaine or atropine and aßter deprivation (1) .
The same amount oß tension developed
in response to Ca++ depletion regardless oß whether K+ was
Vol. 9, No. 7
RELAXATION OF SKELETAL MUSCLE
externally present (Fig, lA) or absent (Fig, 1D, B, C),
417 without
external B+ the rate oß tension rise appeared Blower but was not aarkedly changed (Fig . 1) .
Potassiu= deprivation in Bast muscles
produces a lowered internal H+ (8, 9, 10) .
Iß this occurs in slow
ßibers then neither ezterael nor internal H+ would have any appreciable ßunction in the development oß tension during Ca++ loss . In contrast to the lack oß eßßect oß external H+ on tension induced by Ca ++ loss, the relaaation rate upon return oß Ca ++ was markedly decreased by the prior H+ depletion and continued absence oß B+ (Fig . 1),
Aßter 18 hours oß H+ depletion the average
maximal rate oß relaxation when Ca ++ was returned without H+ was 0 .17 grams/min and aßter 10 minutes oß Ca ++ was 0 .07 grams/min (làble I), TAHLB I
THE RATE OF RELAXATION OF K+ DEPRIVED SLOW STRIATED FROG MUSCLE K+
depletion (hours) 1 .5
16
Number muscle reponses
Maximal mts . Return of Ca++ (no K+) yms/min
Rate after 10 a 30 min . of Ca++ (no K+) yms/min
Maximal rats. Retum of K+ (Cam present) qms/min
_36 53
0.11 ±,01 (2.4 ± .13)
0.03± .O1 (30 min.)
0.371 .05 (1 .4 t .11)**
_10 20
0.17 ±.02 (2.6 ± .15)*
0.07 ±.Ol (10 min.)
2.50 ± .50 (1,8 1 .18)**
* Grams of tension developed before relaxation ** Grams of tension of point of K+ return when leßt with Ca ++ but without H+ ßor longer than 10 ainutes the muscles failed to relax and tensions were maintained ßor long periods (Fig, 1-B),
without R+ deprivation the same =uncles
418
RELAXATION OF SKELETAL MUSCLE
Vol. 9, No. 7
(Table I, lower) relaxed at a rate oß 0 .53 grams/min when Cam+ was returned,
When the muscles had been deprived oß H+, and Ca ++ had
been withdrawn ßor 20 minutes and then returned for 10 minutes, the subsequent return oß H+ relaxed the muscles at an average maximal rate oß 2,5 grams/min (Table I) .
This rate is 35 times as
fast as the muscle had been relaxing immediately beßore the return oß H+ (0,07 gm/min), and ßive times as fast as when Ca ++ was returned in the presence oß H+ (0,53 gm/min),
The slower relax-
ation when Cam was returned in the presence oß H+ may indicate that under these conditions Ca m re-eatrq limits the rate oß relaxation,
Muscles deprived oß H+ for only 1 .5 hours showed the
same dependency on H+ ßor relaxation as the muscles subjected to 16 hours oß deprivation (Table I) .
The slower rate oß relaxation
upon return oß H+ aßter only 1 .5 hours of H+ deprivation may have been due to less H+ depletion, the longer period oß Ca ++ return without H+, or the extended period oß Ca ++ depletion,
The experi-
nents of both groups demonstrate is two ways that the relaxation oß slow muscle depends to a great extent on the external R+ ions : (1)
lfider ionic conditions that permit complete and rapid relax-
ation is the presence oß physiological amounts oß H+ , the absence oß H+ permits only a slow and partial relaxation, (2)
When slow
muscle is maintaining tension without external H+ the return oß H* at a physiological concentration induces a . rapid and complete relaxation, Discussion Another study showed that the tension induced iß sloa .muscle by Cam deprivation depends on external monovalent cations that can penetrate the muscle membrane (11) .
When external Na + was
replaced by organic monovalent cations that were non-penetrant (Tris or 2-amino-2-methyl-1, 3 propanediol at pH 7,2) tension
Vol . 9, No. 7
RELAXATION OF SKELETAL MUSCLE
Bailed to develop due to Ca ++ lack .
419
Substituting Na + ßor the non-
penetrant canons during the Ca++ depletion led to a prompt development oß tension .
The subsequent replacement oß the Na + by
the non-penetrating canons led to a rapid relaxation (11) .
This
relaxation occurred presumably because there was no Na + to enter the muscle ßiber to maintain tension while the Na+ inside was being rapidly lost to the external ßluid .
The muscle would now
be in a state oß relaxation under Ca ++ depletion because oß no external Na + just as when Ca ++ was removed aßter substitution oß Na + by non-penetrant canons .
The experiments just mentioned
indicate that entry oß Na+ into some muscle compartment is necessary ßor the development oß tension due to Ca ++ lack .
They
further show that without external sodium available ßor entry the tension Could not be maintained .
Since tension disappears when
tb,ere is no external Na + and because the entry oß Na + is implicated in tension development it is probable that in slow muscle Na + eßßlux is necessary ßor relaxation . Because oß the Bindings stated above, the R+-deprived muscles in contractors due to Ca ++ lose can be considered to contain excess internal Na + ; its removal would appear necessary ßor relaxation .
Iß the same transport conditions prevail in slow
muscle that do in fast, i .e ., that Na + efßlua is in part dependent on external R~ then the absence oß H+ and the subsequent ßailure oß Na + to leave the slow muscle ßibers would explain the ßailure oß the slow ßibers to relax .
Since there are no muscles known
that contain only slow ßibers no information is available ßrom slow fibers as to ionic ßlvaes or contents .
Unknown ßor the same
reason is whether the Na +-R+ activated ATPase is present in slow ßiber membranes as it is in the Bast .
Providing transport ATPase
ßunctions is slow ßibers as it does in other cells, and iß ex-
420
RELAXATION OF SKELETAL MUSCLE
Vol . 9, No. 7
ternal K+ aßßects Na + transport in slow as it does is Bast muscle (3, 4, 5), then the potassium dependent relaxation described here gould be adequately eaplained by relaxation depending on enzymatic transport . St~mar y 81ow-type skeletal muscle ßibers deprived oß K+ aad made to contract by Ca++ depletion ßa11 to relax completely when Ca ++ is returned,
Return oß external K+ , known to increase Na + trans-
port in muscle and to activate transport ATPase, induces a rapid and complete relaxâtion . Reßerences 1,
R, L, IRWIN and M, M, Hein, J . Gen . Physiol . 47, 133 (1963) .
2.
R . L . IRWIN and M . M. Hein, Am . .I . Physiol . 211,1117 (1986),
3,
R, D, HEYNEB, Pros . Roy . Soc, B .
4,
P, HOROWICZ and C, J, GERBER, J . Gen. Physiol . 48, 489 (1985), s aad A, STIENHARDT, Physiol . 198, 581 R, D, HEYNES R, J.
5,
142, 359 (1954) .
(1968) . ß.
I, M . GLYNN, J. Physiol . 160, 18P (1982),
7,
R . WSITTAH, Biocäem . .I . 84, 110 (1982) .
$.
E, J, HARRIS',
9.
H, B, BTEINBACH, J . Biol . Chem . 133, 895 (1940) .
10 .
J. Physiol . 177, 355 (1965),
R, A . BJODIN and L . A . BEAUGE, J. Gea, Physiol . 52, 389 (1988) ,
11 .
R. L . IRWIN and H, L, OLIVER, Am . J. Physiol . 217, 13 (1989) .