Induction of inward rectifiers in mouse skeletal muscle fibres in culture

✍ Scribed by Tohru Gonoi; Shuji Hasegawa

• Publisher: Springer
• Year: 1991
• Tongue: English
• Weight: 529 KB
• Volume: 419
• Category: Article
• ISSN: 0031-6768
• DOI: 10.1007/bf00370311

✦ Synopsis

The whole-cell voltage-clamp technique was used to study the physicochemical nature and regulatory mechanisms of inward rectifier K + currents in skeletal muscle fibres (flexor digitorum brevis muscle) of newborn mice. The inward rectifier K + currents were at hardly discernible levels (_ 15 pA/cm 2) in fibres acutely isolated from 1-day-old (PI) mice or P1 fibres cultured without any added reagents for 1-3 days. When A23187 (1 ~M), ionomycin (3 ~tM) or ryanodine (_>0.03 ~tM) was added to a culture medium, a significant increase of the inward rectifier current (-106_+46 ~tA/cm 2 at a membrane potential of -100mV and an extracellular K + concentration of 20 mM for the case of A23187) was observed within 1 day after the addition of the reagents. The inward rectifier current decreased to the level of control cultures within 11 h after a removal of A23187. The increase of the current with A23187 was iLnhibited with actinomycin D, cycloheximide or colchicine, but not with tunicamycin or cytochalasin B. We suggest that the functional inward rectifiers are induced in skeletal muscle fibres by elevation of the cytosolic Ca 2+ concentration in a transcription and protein synthesis dependent manner and that the microtubular system is necessary for this induction.