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Proportionale Aktivierung von ATPase-Aktivität und Kontraktionsspannung durch Calciumionen in isolierten contractilen Strukturen verschiedener Muskelarten

Proportionale Aktivierung von ATPase-Aktivität und Kontraktionsspannung durch Calciumionen in... “Isolated” contractile Actomyosinsystems (i.e. glycerolextracted musclefibres) were suspended in ATP-saltsolutions. A graded increase in calcium-ionconcentration (using Calcium-EGTA-buffers) from 10−8–10−7 M to 10−6–10−5 M lead to a graded and proportional increase of tension and ATPase activity without ratelimitation by diffusional processes. The Calciumconcentration for 50% activation (calcium sensitivity) ranges from 10−7 M to 10−6 M at pH 7 in actomyosinsystems of the following muscles: Fibrillar and non-fibrillar muscles of waterbugs including Lethocerus maximus, rabbit sceletal muscle, dog-heart papillary muscle, guinea pig taenia coli, byssus retractor of mytilus edulis (ABRM), cow carotide artery. The calciumthreshold is about 10–100 smaller than the concentration required for maximal activation. Replacement of K ions by Na ions and a increase in the free Mg++ concentration from 10−5 M to 10−3 M as well as the degree of stretchactivation (in fibres of insect fibrillar muscle) had no effect on the calcium sensitivity while a decrease in pH from 7,0 to 6,0 decreased the calciumsensitivity 2× in ABRM and rabbit sceletal muscle, 10× in the heart and 80× in insect muscle. The thresholdconcentration for tension activation is slightly larger than that for ATPase activation, but the ratio of tensionincrease and increase in ATPase activity is a constant (the holding economy) which is independent of calciumconcentration and pH and in tonic smooth muscle this constant is at least 10 times smaller than in striated muscle. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Pflügers Archiv European Journal of Physiologyl of Physiology Springer Journals

Proportionale Aktivierung von ATPase-Aktivität und Kontraktionsspannung durch Calciumionen in isolierten contractilen Strukturen verschiedener Muskelarten

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References (39)

Publisher
Springer Journals
Copyright
Copyright © 1967 by Springer-Verlag
Subject
Biomedicine; Human Physiology; Molecular Medicine; Neurosciences; Cell Biology; Receptors
ISSN
0031-6768
eISSN
1432-2013
DOI
10.1007/BF00363480
Publisher site
See Article on Publisher Site

Abstract

“Isolated” contractile Actomyosinsystems (i.e. glycerolextracted musclefibres) were suspended in ATP-saltsolutions. A graded increase in calcium-ionconcentration (using Calcium-EGTA-buffers) from 10−8–10−7 M to 10−6–10−5 M lead to a graded and proportional increase of tension and ATPase activity without ratelimitation by diffusional processes. The Calciumconcentration for 50% activation (calcium sensitivity) ranges from 10−7 M to 10−6 M at pH 7 in actomyosinsystems of the following muscles: Fibrillar and non-fibrillar muscles of waterbugs including Lethocerus maximus, rabbit sceletal muscle, dog-heart papillary muscle, guinea pig taenia coli, byssus retractor of mytilus edulis (ABRM), cow carotide artery. The calciumthreshold is about 10–100 smaller than the concentration required for maximal activation. Replacement of K ions by Na ions and a increase in the free Mg++ concentration from 10−5 M to 10−3 M as well as the degree of stretchactivation (in fibres of insect fibrillar muscle) had no effect on the calcium sensitivity while a decrease in pH from 7,0 to 6,0 decreased the calciumsensitivity 2× in ABRM and rabbit sceletal muscle, 10× in the heart and 80× in insect muscle. The thresholdconcentration for tension activation is slightly larger than that for ATPase activation, but the ratio of tensionincrease and increase in ATPase activity is a constant (the holding economy) which is independent of calciumconcentration and pH and in tonic smooth muscle this constant is at least 10 times smaller than in striated muscle.

Journal

Pflügers Archiv European Journal of Physiologyl of Physiology – Springer Journals

Published: Sep 7, 2004

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