ION CHANNELS IN A SKELETAL-MUSCLE CELL-LINE FROM A DUCHENNE MUSCULAR-DYSTROPHY PATIENT

A cell line (RCDMD), derived from a muscle biopsy taken from a 7-year- old patient with Duchenne muscular dystrophy (DMD), was established in vitro using conditioned media from the UCHT1 thyroid cell line as des cribed elsewhere (Biochim Biophys Acta 1992;1134:247-255). Unlike othe r cell lines established by the same procedure, RCDMD cells were highl y refractory to transformation and the resulting cell line grew slowly with a doubling time of approximately 72 h. Further, cells continue t o grow after more than 20 doublings and 15 passages. Some of the chara cteristics of the cell line include lack of reaction with antidystroph in antibodies and the presence of receptors for the dihydropyridine PN 200-110 (K-d) = 0.3 +/- 0.05 nmol/L and B-max = 1.06 +/- 0.03 pmol/mg protein) and for alpha-bungarotoxin (K-d = 1.02 +/- 0.17 nmol/L and B- max = 4.2 +/- 0.37 pmol/mg protein). Patch clamped cells in the voltag e clamp configuration lack ion currents when growing in complete mediu m with high serum, but they can be induced to differentiate by serum d eprivation and addition of hormones and trace elements. After 5 days i n differentiating medium, noninactivating, delayed rectifier potassium currents are seen. At day 12, A-type, inactivating potassium currents as well as transient inward currents are seen. In conditions in which sodium and potassium currents are absent, a very fast activating and fast inactivating calcium current was evident. The cell line offers th e possibility of studying cellular mechanisms in the pathophysiology o f DMD. (C) 1994 John Wiley & Sons, Inc.