Calcium dependence of electrical and mechanical activity in rat ileum examined by the sucrose-gap technique

Mahmod, S.M.; Huddart, H.

doi:10.1016/0742-8413(93)90075-v

Cited by 1 publication

(2 citation statements)

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“…This A23187‐induced contraction was inhibited at almost the same concentrations required to reduce the high‐K+‐induced response by nifedipine, D‐600 or verapamil in taenia coli ( Nasu & Magami, 2000), ileum ( Rosenberger & Triggle, 1979) and aorta ( Watson, 1978). Mahmod & Huddart (1993) showed that in the rat ileum, A23187 increased the plateau phase of the action potential dependent upon an influx of extracellular Ca2+ by several mV. This suggested that A23187 produced contractions by increasing Ca2+ influx through dihydropyridine‐sensitive Ca2+ channels in smooth muscle cell membranes.…”

Section: Discussionmentioning

confidence: 99%

“…The carboxylic acid ionophore A23187 forms an electroneutral complex with Ca2+, and the Ca2+‐ionophore complex is transported into the organic phase from the aqueous phase across artificial membranes ( Puskin & Gunter, 1975) or biological membranes of mitochondria ( Wong, Wilkinson, Hamill & Horings, 1973; Dransfield & Aprille, 1993), the sarcoplasmic reticulum ( Caswell & Pressman, 1972; Burges et al ., 1991 ) and mast cells ( Foreman, Mongal & Gomperts, 1973; Vilarino, Vieytes, Vieties & Bontana, 1999). A23187 has been shown to induce contractions dependent on external Ca2+ in smooth muscles, such as those of the stomach ( Mandrek & Golenhofen, 1977), ileum ( Rosenberger & Triggle, 1979; Mahmod & Huddart, 1993), taenia coli ( Mandrek & Golenhofen, 1977; Nasu & Magami, 2000), aorta ( Watson, 1978; Kawahara, Izumi, Okada & Izawa, 1996) and vas deferens ( Ishida & Shibata, 1980).…”

Section: Introductionmentioning

confidence: 99%

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Metabolic dependency of ionophore A23187‐induced contraction of ileal longitudinal smooth muscle

Nasu

Nishikawa

2000

J. Autonom. Pharmacol.

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1. Tonic contraction in response to K+ is well known to be highly dependent on aerobic metabolism in ileal muscle. The ionophore A23187 (10(-5) M) induced an initial contraction and successive rhythmic contraction in ileal muscle, but did not induce tonic contraction. This study, therefore, was performed to investigate the metabolic dependency during contraction induced by A23187. 2. Under hypoxic conditions, A23187 (10(-5) M) induced an initial contraction accompanied by an increase in lactate release. However, it induced only small rhythmic contractions and decreases in ATP, phosphocreatinine (PCr) and glycogen contents. 3. In glucose-free medium, A23187 (10(-5) M) induced an initial contraction and concomitant significant decrease in the ATP and glycogen contents. However, it did not induce successive rhythmic contractions. In 'glycogen-depleted muscle' stimulated repeatedly with 60 mM K+ in glucose-free medium, 60 mM K+ induced a phasic contraction without tonic contraction. A23187 induced no contraction under these conditions. 4. These results suggested that the initial contraction induced by A23187 was dependent on endogenous glycogen, while successive rhythmic contractions were dependent on aerobic metabolism after supply of external glucose to the ileal muscle.

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