Effects of amrinone on the electromechanical coupling in frog skeletal muscle fibres

• The contractile effects of I.I mM amrinone were studied on isolated skeletal muscle fibres of the frog (2–5 °C, slack length). Amrinone potentiated the twitch amplitude and the maximum tetanic tension and also enhanced the maximum contracture response elicited by 117.5 mM K+ (mean increase 6.3 ± 1.8 %, n = 6, P < 0.02). The time to halfrelaxation of the potassium contracture was slightly increased (mean change 13.8 ± 3.5%, n = 7, P < 0.01). Amrinone furthermore shifted the S-shaped curve relating contracture tension to log K+ to the left, and thus reduced the threshold depolarization (the mechanical threshold needed) to elicit a contracture (mean reduction 11 ± 1 mV). The duration of the action potential at the –25 mV level was slightly increased by amrinone, whereas the resting membrane potential was unaffected. 

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MEDICINE

MEDICIN

Biomedicinsk vetenskap

Biomedical Sciences

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