Abstract
1. In order to clarify the mechanism of contracture on cooling of caffeine-treated intact muscle fibres, the temperature dependence of a calcium (Ca2+) release mechanism, 'Ca2+-induced Ca2+ release', of the sarcoplasmic reticulum (SR) was examined in skinned frog muscle fibres. 2. Skinned fibres in a solution containing 1.2 mM-caffeine and 0.7 mM-EGTA (Mg2+, 1.5 mM, Mg-ATP, 3.5 mM, pH 7), contracted on cooling (from 22 to 2 degrees C) due to Ca2+ release from the SR. 3. The rate of Ca2+ release from skinned fibre SR in a medium which contained Ca2+ ions (with 10 mM-EGTA) and no ATP salts, was determined under various conditions using the 'caffeine method.' 4. In the absence of Mg2+ ions, adenine nucleotides and caffeine, the rates at room temperature (21-22 degrees C) were 3-4 times greater than those at a lower temperature (1.5-3 degrees C), at any concentrations of Ca2+ ions external to the SR. 5. In the presence of Mg2+ ions (1.5 mM) and beta,gamma-methylene ATP (1 mM), the effect of temperature on the rates disappeared in Ca2+-containing media, although the effect remained in Ca2+-free medium. 6. When caffeine (1.2 mM), which is a potentiator of the Ca2+-induced Ca2+ release, was added to the test medium with Mg2+ and beta,gamma-methylene ATP, the resulting potentiating effect was several times greater than that at lower temperature. 7. In order to examine the temperature dependence of the Ca2+ pump activity of the SR, the initial rate of Ca2+ uptake by the empty SR was determined under various conditions in the presence of Mg2+ ions (1.5 mM) and Mg-ATP (3.5 mM). The Q10 of the pump activity was around 2.0 at the Ca2+ ion concentrations examined (less than 10(-6) M). 8. A numerical model based on the results obtained, together with some reasonable assumptions, suggested that both suppression of the Ca2+ pump and enhancement of the Ca2+ release contribute to the cooling contracture of caffeinized fibres.
Full text
PDFSelected References
These references are in PubMed. This may not be the complete list of references from this article.
- Baylor S. M., Chandler W. K., Marshall M. W. Optical measurements of intracellular pH and magnesium in frog skeletal muscle fibres. J Physiol. 1982 Oct;331:105–137. doi: 10.1113/jphysiol.1982.sp014367. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Baylor S. M., Chandler W. K., Marshall M. W. Sarcoplasmic reticulum calcium release in frog skeletal muscle fibres estimated from Arsenazo III calcium transients. J Physiol. 1983 Nov;344:625–666. doi: 10.1113/jphysiol.1983.sp014959. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Horiuti K. Some properties of the contractile system and sarcoplasmic reticulum of skinned slow fibres from Xenopus muscle. J Physiol. 1986 Apr;373:1–23. doi: 10.1113/jphysiol.1986.sp016032. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Kakuta Y. Effects of ATP and related compounds on the Ca-induced Ca release mechanism of the Xenopus SR. Pflugers Arch. 1984 Jan;400(1):72–79. doi: 10.1007/BF00670539. [DOI] [PubMed] [Google Scholar]
- Konishi M., Kurihara S., Sakai T. Change in intracellular calcium ion concentration induced by caffeine and rapid cooling in frog skeletal muscle fibres. J Physiol. 1985 Aug;365:131–146. doi: 10.1113/jphysiol.1985.sp015763. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Ogawa Y. Some properties of fragmented frog sarcoplasmic reticulum with particular reference to its response to caffeine. J Biochem. 1970 May;67(5):667–683. doi: 10.1093/oxfordjournals.jbchem.a129295. [DOI] [PubMed] [Google Scholar]
- Smith J. S., Coronado R., Meissner G. Sarcoplasmic reticulum contains adenine nucleotide-activated calcium channels. Nature. 1985 Aug 1;316(6027):446–449. doi: 10.1038/316446a0. [DOI] [PubMed] [Google Scholar]
- Weber A., Herz R. The relationship between caffeine contracture of intact muscle and the effect of caffeine on reticulum. J Gen Physiol. 1968 Nov;52(5):750–759. doi: 10.1085/jgp.52.5.750. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Weber A. Regulatory mechanisms of the calcium transport system of fragmented rabbit sarcoplasmic rticulum. I. The effect of accumulated calcium on transport and adenosine triphosphate hydrolysis. J Gen Physiol. 1971 Jan;57(1):50–63. doi: 10.1085/jgp.57.1.50. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Yount R. G., Babcock D., Ballantyne W., Ojala D. Adenylyl imidodiphosphate, an adenosine triphosphate analog containing a P--N--P linkage. Biochemistry. 1971 Jun 22;10(13):2484–2489. doi: 10.1021/bi00789a009. [DOI] [PubMed] [Google Scholar]