TMB-8 can block twitches without blocking high K+ or caffeine induced contractures in frog's skeletal muscle.

Abstract

TMB-8 [8-(diethylamino)-octyl-3,4,5-trimethoxybenzoate] is known to inhibit calcium ion dependent processes in several tissues by stabilizing some intracellular stores of membrane-bound calcium. TMB-8 was used to study the excitation-contraction (E-C) coupling process in frog's skeletal muscle. TMB-8 (5 X 10(-5) - 10(-4) M) blocked electrically evoked twitches but not high K+ (123 mM)- or caffeine (2.36 mM)-induced contractures in isolated, curarized toe muscles. TMB-8 (10(-4) M) produced a small decrease (16%) in the action potential of frog's sartorius muscle fibres. However, reducing extracellular Na+ to 44.7 mM produced a similar reduction (17%) in action potential amplitude but did not suppress the twitch; i.e. it produced only a small increase (about 10%) in twitch amplitude. It is known that potassium contractures are produced by extracellular Ca++ ions which enter through calcium channels in the t-tubules and that caffeine produces contractures by sensitizing the sarcoplasmic reticulum to Ca++-induced Ca++ release. The present results suggest that TMB-8 blocks twitches by preventing the release of Ca++ ions bound to the intracellular surface of the t-tubular membrane which is often called the store of 'trigger-calcium' ions.

• Authors: S S Shetty, S S Rizvi, G B Frank
• Journal: Life sciences (Life Sci) Vol. 39 Issue 13 Pg. 1137-41 (Sep 29 1986) ISSN: 0024-3205 [Print] Netherlands
• PMID: 3489151 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Caffeine
• 8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate
• Gallic Acid
• Potassium
• Calcium

Topics

• Action Potentials (drug effects)
• Animals
• Caffeine (pharmacology)
• Calcium (metabolism)
• Gallic Acid (analogs & derivatives, pharmacology)
• In Vitro Techniques
• Muscle Contraction (drug effects)
• Muscles (drug effects)
• Potassium (pharmacology)
• Rana pipiens