title: Depressive effects of free fatty acids on the development of tension in different muscle types.
abstract: The depression of twitch and tetanic tensions, contractures, and spontaneous activities of various muscle preparations by a selected free fatty acid (Na-octanoate, NaC8) depends on the concentration, the temperature, the time of exposure, and the type of muscle. Among skeletal muscles, there is neither a significant difference between frog and rat twitch muscles nor between fast- and slow-twitch rat muscles at room temperature. Small differences seem to occur between frog tonic and phasic fibres as well as between fast- and slow-twitch rat muscles at 32 degrees C. Smooth muscles are more sensitive than skeletal muscles but less sensitive than papillary muscles in which 0.5 mmol/l NaC8 decrease the contractility by about 50%. The different sensitivity of the various muscle types might be caused by unequal alterations of membrane properties responsible for excitation-contraction coupling. It is supposed that free fatty acids interact with the calcium binding sites of the membranes.
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000502:physiology; D002210:Caprylates / Q000378:metabolism / Q000494:pharmacology; D002415:Cats; D005230:Fatty Acids, Nonesterified / Q000378:metabolism / Q000494:pharmacology*; D006321:Heart / Q000502:physiology; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects*; D009132:Muscles / Q000502:physiology; D009200:Myocardial Contraction / Q000187:drug effects*; D011188:Potassium / Q000494:pharmacology; D051381:Rats
chemical_list: D002210:Caprylates; D005230:Fatty Acids, Nonesterified; D002110:Caffeine; D000251:Adenosine Triphosphatases; C031492:octanoic acid; D011188:Potassium; D002118:Calcium