Abstract
Chloride-induced Ca release in skinned muscle fibers was studied by measuring isometric force transients and 45Ca loss from fiber to washout solutions. Skinned fibers prepared from muscles soaked in normal Ringer solution made large force transients in 120 mM Cl solution with 5 mM ATP and 1 mM Mg, but 3 mM Mg was inhibitory. Mg inhibition was antagonized by low temperature and by Cd, agents which slow active Ca uptake by the sarcoplasmic reticulum (SR). In low Mg++, Cl stimulated rapid 45Ca release from the SR in sufficient amounts to account for the force response. The increased 45Ca release was inhibited by EGTA, suggesting that release requires free Ca under these conditions. The 45Ca initially released was partially reaccumulated later. Reaccumulation was increased in higher Mg++. These results provide additional evidence that the Ca uptake rate is an important determinant of net release, and suggest that Mg++ acts primarily on this mechanism. Skinned fibers prepared from muscles soaked in low Cl solutions could give force responses to Cl solutions with 3 mM and 6 mM Mg. This observation suggests that the Cl stimulus varies with the [Cl] gradient across the internal membranes, and supports the hypothesis that applied Cl causes membrane depolarization.
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Selected References
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- Carvalho A. P. Effects of potentiators of muscular contraction on binding of cations by sarcoplasmic reticulum. J Gen Physiol. 1968 Mar;51(3):427–442. doi: 10.1085/jgp.51.3.427. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Costantin L. L., Podolsky R. J. Depolarization of the internal membrane system in the activation of frog skeletal muscle. J Gen Physiol. 1967 May;50(5):1101–1124. doi: 10.1085/jgp.50.5.1101. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Ebashi S., Endo M., Otsuki I. Control of muscle contraction. Q Rev Biophys. 1969 Nov;2(4):351–384. doi: 10.1017/s0033583500001190. [DOI] [PubMed] [Google Scholar]
- Endo M., Blinks J. R. Inconstant association of aequorin luminescence with tension during calcium release in skinned muscle fibres. Nat New Biol. 1973 Dec 19;246(155):218–221. doi: 10.1038/newbio246218a0. [DOI] [PubMed] [Google Scholar]
- Ford L. E., Podolsky R. J. Calcium uptake and force development by skinned muscle fibres in EGTA buffered solutions. J Physiol. 1972 May;223(1):1–19. doi: 10.1113/jphysiol.1972.sp009830. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Ford L. E., Podolsky R. J. Intracellular calcium movements in skinned muscle fibres. J Physiol. 1972 May;223(1):21–33. doi: 10.1113/jphysiol.1972.sp009831. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Ford L. E., Podolsky R. J. Regenerative calcium release within muscle cells. Science. 1970 Jan 2;167(3914):58–59. doi: 10.1126/science.167.3914.58. [DOI] [PubMed] [Google Scholar]
- HARRIS E. J. THE CHLORIDE PERMEABILITY OF FROG SARTORIUS. J Physiol. 1965 Jan;176:123–135. doi: 10.1113/jphysiol.1965.sp007539. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Inesi G. Active transport of calcium ion in sarcoplasmic membranes. Annu Rev Biophys Bioeng. 1972;1:191–210. doi: 10.1146/annurev.bb.01.060172.001203. [DOI] [PubMed] [Google Scholar]
- Kasai M., Miyamoto H. Depolarization induced calcium release from sarcoplasmic reticulum membrane fragments by changing ionic environment. FEBS Lett. 1973 Aug 15;34(2):299–301. doi: 10.1016/0014-5793(73)80816-6. [DOI] [PubMed] [Google Scholar]
- MacLennan D. H. Purification and properties of an adenosine triphosphatase from sarcoplasmic reticulum. J Biol Chem. 1970 Sep 10;245(17):4508–4518. [PubMed] [Google Scholar]
- Nakajima Y., Endo M. Release of calcium induced by 'depolarisation' of the sarcoplasmic reticulum membrane. Nat New Biol. 1973 Dec 19;246(155):216–218. doi: 10.1038/newbio246216a0. [DOI] [PubMed] [Google Scholar]
- Rapoport S. I. A fixed charge model of the transverse tubular system of frog sartorius. J Gen Physiol. 1969 Aug;54(2):178–187. doi: 10.1085/jgp.54.2.178. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Rapoport S. I., Peachey L. D., Goldstein D. A. Swelling of the transverse tubular system in frog sartorius. J Gen Physiol. 1969 Aug;54(2):166–177. doi: 10.1085/jgp.54.2.166. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Stephenson E. W., Podolsky R. J. Regulation by magnesium of intracellular calcium movement in skinned muscle fibers. J Gen Physiol. 1977 Jan;69(1):1–16. doi: 10.1085/jgp.69.1.1. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Winegrad S. Intracellular calcium movements of frog skeletal muscle during recovery from tetanus. J Gen Physiol. 1968 Jan;51(1):65–83. doi: 10.1085/jgp.51.1.65. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Yamada S., Sumida M., Tonomura Y. Reaction mechanism of the Ca2+-dependent ATPase of sarcoplasmic reticulum from skeletal muscle. 8. Molecular mechanism of the conversion of osmotic energy to chemical energy in the sarcoplasmic reticulum. J Biochem. 1972 Dec;72(6):1537–1548. doi: 10.1093/oxfordjournals.jbchem.a130045. [DOI] [PubMed] [Google Scholar]