Abstract
The force of contractures produced by 14-400 mM-K+ (as methanesulphonate) was measured in whole mouse soleus (sol.), extensor digitorum longus (e.d.l.), and in bundles from these muscles. Frog semitendinosus muscles were used for comparison. Whole mouse muscles displayed biphasic contracture responses lasting more than 5 min when provoked by 150m M-K+. Contractures of bundles dissected from these muscles were monophasic and had a short duration. The time required for the muscle bundles to contract and relax to 1/2 maximum force (T) was an inverse function of [K+]. T was increased by lowering [K+] from 400 to 50 mM by a factor of 8.3 and 7.0 in proximal and distal portions of sol. and by a factor of 4.2 and 2.8 in proximal and distal portions of e.d.l., respectively. The force-[K+] relation was steeper for sol. than for e.d.l., and the proximal portions were more sensitive to K+ than the distal portions, particularly in e.d.l. The capability of the muscles to produce force in response to 400 mM-K+ after a 10 min exposure to 30 or 50 mM-K+ was high in sol., somewhat lower in proximal parts of e.d.l. and in frog semitendinosus, and lowest in distal parts of e.d.l. It was concluded that K contractures of mouse muscles are basically monophasic, and that biphasic contractures of whole muscles arise because of K+-diffusion delays, slow responses to intermediate [K+], and differences in responsiveness of the fibres contained in a particular muscle.
Full text
PDF
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Dulhunty A. F. Potassium contractures and mechanical activation in mammalian skeletal muscles. J Membr Biol. 1980 Dec 30;57(3):223–233. doi: 10.1007/BF01869590. [DOI] [PubMed] [Google Scholar]
- Dulhunty A. F. Slow potassium contractures in mouse limb muscles. J Physiol. 1981 May;314:91–105. doi: 10.1113/jphysiol.1981.sp013693. [DOI] [PMC free article] [PubMed] [Google Scholar]
- HODGKIN A. L., HOROWICZ P. Potassium contractures in single muscle fibres. J Physiol. 1960 Sep;153:386–403. doi: 10.1113/jphysiol.1960.sp006541. [DOI] [PMC free article] [PubMed] [Google Scholar]
- LORKOVIC H. Potassium contracture and calcium influx in frog's skeletal muscle. Am J Physiol. 1962 Mar;202:440–444. doi: 10.1152/ajplegacy.1962.202.3.440. [DOI] [PubMed] [Google Scholar]
- Lewis D. M., Parry D. J., Rowlerson A. Isometric contractions of motor units and immunohistochemistry of mouse soleus muscle. J Physiol. 1982 Apr;325:393–401. doi: 10.1113/jphysiol.1982.sp014157. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Lorković H. Membrane potential and mechanical tension in white and red muscles of the rat. Am J Physiol. 1971 Oct;221(4):1044–1050. doi: 10.1152/ajplegacy.1971.221.4.1044. [DOI] [PubMed] [Google Scholar]