The recovery from the relaxant effect by ouabain and the metabolic dependency of K+ contractions in guinea-pig taenia coli.
1. Ouabain (2.5 x 10(-5) M) inhibited preferentially the tonic response to 40 mM K+ medium (containing enough Na+) without affecting the phasic in taenia coli. When 11 mM lactate was added to the medium (pH 6.5) in the presence of ouabain, the tonic phase to 40 mM K+ recovered markedly. 2. Ouabain (2.5 x 10(-5) M) did not affect the tonic tension in 152 mM K+ medium (Na+ 0 mM). However, ouabain inhibited the recovered tension by the addition of 50 mM Na+ in the 152 mM K+ medium. But ouabain failed to inhibit the marked recovered tension by the addition of 11 mM lactate which utilized, even in the absence of external Na+, in 152 mM K+ medium. 3. Ouabain partly inhibited the shortening to 40 mM K+ (containing enough Na+) at light load; however, it inhibited markedly the shortening at heavy load. 4. There is a possibility that ouabain inhibits active transport of glucose depending on external Na+ in taenia coli of smooth muscle. Ouabain could not inhibit the tension by lactate which utilized under conditions of independent on Na+. Furthermore, it is suggested that ouabain inhibits the contraction which depends on aerobic metabolism; however, it has only a slight effect on contraction which depends on aerobic metabolism; however, it has only a slight effect on contraction which was not so dependent on aerobic metabolism.
Department of Veterinary Pharmacology, Faculty of Agriculture, Yamaguchi University, Japan.
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Nasu
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Zakimi
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Shibata
D000818:Animals; D003106:Colon / Q000187:drug effects* / Q000502:physiology; D006168:Guinea Pigs; D006863:Hydrogen-Ion Concentration; D007552:Isotonic Solutions; D007700:Kinetics; D007773:Lactates / Q000378:metabolism / Q000494:pharmacology; D019344:Lactic Acid; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009126:Muscle Relaxation / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology; D009994:Osmolar Concentration; D010042:Ouabain / Q000494:pharmacology*; D011188:Potassium / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D011773:Pyruvates / Q000378:metabolism; D019289:Pyruvic Acid; D012964:Sodium / Q000494:pharmacology
D007552:Isotonic Solutions; D007773:Lactates; D011773:Pyruvates; D019344:Lactic Acid; D010042:Ouabain; D019289:Pyruvic Acid; D012964:Sodium; D011188:Potassium