Action of heptaminol hydrochloride on contractile properties in frog isolated twitch muscle fibre.
1. Heptaminol stopped or delayed the progressive decline in tension which characterizes the phenomenon of fatigue in frog isolated twitch muscle fibre. 2. Heptaminol had no action on the sodium, potassium and calcium voltage-dependent ionic conductances. 3. The hypothesis of an action via an internal alkalinization was tested by comparison with the action of NH4Cl. Both substances increased the tension. 4. The action of heptaminol was suppressed in sodium-free (TRIS) solution or in the presence of amiloride while the action of NH4Cl was always observed. 5. These results could be explained by a stimulation of the Na/H antiport by heptaminol.
Allard
B
B
Laboratoire de Physiologie des Eléments Excitables (CNRS UA 180), Université Claude Bernard Lyon I, Villeurbanne, France.
Jacquemond
V
V
Lemtiri-Chlieh
F
F
Pourrias
B
B
Rougier
O
O
D000200:Action Potentials / Q000187:drug effects; D000584:Amiloride / Q000494:pharmacology; D000643:Ammonium Chloride / Q000494:pharmacology; D000818:Animals; D004558:Electric Stimulation; D005221:Fatigue / Q000503:physiopathology; D006535:Heptaminol / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D007473:Ion Channels / Q000187:drug effects; D007537:Isometric Contraction / Q000187:drug effects; D009119:Muscle Contraction / Q000187:drug effects; D009132:Muscles / Q000166:cytology / Q000187:drug effects*; D011893:Rana esculenta; D013779:Tetrodotoxin / Q000494:pharmacology
D007473:Ion Channels; D000643:Ammonium Chloride; D006535:Heptaminol; D013779:Tetrodotoxin; D000584:Amiloride