Experiments on the Mechanism of Action of Chlorocresol and Caffeine

Abstract

Phenols are known to cause contraction of skeletal muscle. Thus Torda & Wolff (1945a) reported that phenol (1 mg/ml.) caused a contraction of the frog rectus abdominis muscle, and Cori & Cori (1936) and Barnes, Duff & Threlfall (1955) showed that 2,4-dinitrophenol contracted frog skeletal muscle, and the latter also showed that this substance caused a contraction of the isolated diaphragm which was not abolished when the muscle was depolarized with potassium sulphate. Chlorinated phenols, containing from two to five chlorine atoms, cause a contraction of the isolated diaphragm of the rat (Farquharson, Gage & Northover, 1958).The present experiments locate the site of contraction of chlorocresol in the skeletal muscle of the frog to an energy transfer system probably involving calcium ions, and compare its action with that of caffeine which causes contraction without affecting the membrane potential of the muscle cell (Axelsson & Thesleff, 1958), by a process probably involving the release of calcium ions (Bianchi, 1961;Frank, 1962). METHODSThe rectus abdominis muscle from the frog (Rana temporaria or esculenta) was mounted in a 2-ml. organ-bath containing frog-Ringer solution at room temperature (18 to 220 C) bubbled with oxygen, and arranged to record longitudinal isotonic contractions. The lever had a magnification of five-times and a load of 0.6 to 1.0 g. The frog-Ringer solution had the following composition (g/l.): NaCl 6.54, KCI 0.18, NaHCO3 0.20, NaH2PO4 0.001, CaCl2 0.12 and glucose 2.00. Dose/response relations were obtained for the agonists studied and the responses were repeated in the presence of antagonists, after the preparation had been immersed for 30 min in frog-Ringer solution containing them. Maximal contractions were obtained to acetylcholine (500 jug/ml.).Acetylcholine chloride, caffeine base, chlorocresol, NN-di-isopropylphosphodiamidic fluoride (mipafox), dyflos, sodium edetate, fructose 1,6-diphosphate, gallamine triethiodide, glucose 1-phosphate, iodoacetic acid, potassium chloride, potassium cyanide, procaine hydrochloride, sodium fluoride and tubocurarine hydrochloride were used. All drugs are expressed in pg of base per ml. of frog-Ringer solution, except mipafox which is expressed as the salt. RESULTSAction of chlorocresol. Chlorocresol caused a slow contraction of the rectus abdominis muscle. The threshold was about 50 pg/ml., and there was a good dose/response relation--ship, but contractions to concentrations of chlorocresol higher than 500 ,g/ml. were followed by incomplete relaxations; washing the preparation repeatedly with fresh frog-Ringer solution for 30 min did not always ensure relaxation (Fig. 1), though further washing pro-

Synthetic localized calcium transients directly probe signalling mechanisms in skeletal muscle

“…2000; Treves et al 2002). Moreover, 4‐CMC is known to affect other targets inside muscle cells (Biggs, 1965; Al‐Moussa & Michelangeli, 2009). We did not carry out tests in the presence of caffeine or 4‐CMC alone.…”

Chlorpromazine-Induced Contracture of Frog Rectus Abdominis Muscle

“…Chlorocresol is believed to contract skeletal muscle by altering energy production cycles in muscle (Biggs, 1965). High concentrations o f chlorproma zine could act similarly since the drug inhibits many enzymes and oxidative phosphorylation (Jarvik, 1965;Crossland, 1971).…”