Serum factor induces selective increase in Na-channel expression in cultured skeletal muscle

✍ Scribed by Chaya Brodie; S. R. Sampson

• Publisher: John Wiley and Sons
• Year: 1991
• Tongue: English
• Weight: 681 KB
• Volume: 148
• Category: Article
• ISSN: 0021-9541
• DOI: 10.1002/jcp.1041480106

✦ Synopsis

We have examined effects of horse serum (HS) and various fractions (1 million-lM, 300K, 100K, and 30K nominal molecular weight limit) obtained by ultrafiltration on expression of TTX-sensitive Na-channels and on activities of the Na-K pump and glucose transport systems in cultured myotubes obtained from l-2-day-old neonatal rat pups. Five-day-old cells were transferred to serum-free medium with no hormone or growth factor supplements (DMEM) for 24 hr and then treated with the various serum fractions for 48 hr. Measurements were made of specific [3Hl-saxitoxin (STX) binding, action potential properties, 86Rb-uptake and 2-deoxyglucose (2-DG) uptake. HS significantly increased all parameters compared to DMEM (increases in STX-binding, 69%; Rb-uptake, 65%; 2-DG uptake, 93%). Results of treatment with the separate fractions showed that the 300K fraction caused a significantly greater increase in STX-binding than either HS or the other fractions. In contrast, the increases in Rb and 2-DG uptakes induced by the different fractions were not different from that obtained with HS. We conclude that serum contains a factor that selectively increases expression of TTX-sensitive Na-channels in skeletal muscle.