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골격근 actomyosin superprecipitation에 대한 magnesium ion의 역할에 관한 실험적 연구 : The experimental study on the role of lUg ion on the actomyosin superprecipitation in the skeletal muscle

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Authors

오수명

Issue Date
1974-03
Publisher
서울대학교 의과대학
Citation
Seoul J Med, Vol.15 No.1, pp. 1-8
Abstract
The dissociated actomyosin (clearing of actomyosin)
probably constituted an in vitro model of
resting muscle whereas the fully associated actornyosin(
superprecipitated actomyssin) is analogous to
the active muscle.
In contractile proteins composed of only actin and
myosin, the state of association between the two
proteins can be varied by several factors which are
the changes in the concentrations of ATP, Mg, and
salts. Among them, Mg" " which, in low concentration
behaves as an primary essential factor in the
association of actomyosin, induces the dissociation of
actomyosin in high concentration which is interestingly
the concentration of physiological range.
This biphasic effect of high concentration is still
more obscure in the physiological role of muscular
contraction and relaxation.
In order to elucidate the role of Mg" " in physiological
function of muscle, present study observed the
effect of l\lg-H on actomyosin superprecipitation under
the influence of minute change in Ca ++ concentration
which appears to be a final physiological triggering
in the excitation-contraction coupling.
The results are summarized as follows:
1. ATP induced the superprecipitation of actomyosin
suspension, even when neither Mg++ nor Ca++
was added. Addition of EDTA inhibited the superprecipitation
completely, but this inhibition was reversed
by the addition of Mg"".
2. Inhibition of superprecipitation in condition with
no Mg++ added, was proportional to the concen.
tration of EDTA.
3. Both low and high concentrations of Mg++ inhibited the superprecip.tation but in differert manner;
in the former, the superprecipitation was not
preceded by clearing phase and in the latter, was
preceded by it.
4. The duration of clearing phase was proportional
to Mg++ concentration.
5. The Ca ' " sensitivity of actomyosin to EGTA
was showed only in the presence of Mg!" and also
proportional to Mg"" concentration.
6. It is suggested that Mg" " may have a biphasic
effect in muscle function: it was required for the
onset of superprecipitation as a primary essential
factor but in excess, it gave the actomyosin Ca""sensitivity
which may playa role in muscle relaxation.
ISSN
0582-6802
Language
Korean
URI
https://hdl.handle.net/10371/6601
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