Effects of corticosterone on Ca2+ uptake and myofibrillar disassembly in primary muscle cell culture.
This study was done to examine the effects of corticosterone, a glucocorticoid, on Ca2+ uptake, proteolysis, and Ca2+ channels in primary cultures of chick muscle cells, to clarify the mechanism of glucocorticoid action on muscle proteolysis. Chick muscle cells were incubated for 24 h in a medium containing corticosterone (30 ng/ml) when the cells were confluent (6 days). To examine the contribution of Ca2+ channels, nifedipine, a Ca2+ channels antagonist, was used. Ca2+ uptake measured with 45CaCl2 was increased three-fold by corticosterone, with a peak at 12 h after the treatment started. The growth of the cells estimated from the protein content and creatine kinase activity was not affected by corticosterone. Proteolysis, evaluated with [3H]tyrosine as a label of the protein and Ntau-methylhistidine release, was unchanged by corticosterone. However, the amount of easily releasable myofilament as a measure of myofibrillar disassembly in the muscle cells was increased by corticosterone, and prevented by nifedipine. These results show that corticosterone increases Ca2+ uptake and starts myofibrillar protein breakdown.
United Graduate School of Agricultural Sciences, Kagoshima University, Korimoto 1-21-24, Kagoshima 890-0065, Japan.
Kazue
K
Machida
Ryouji
R
Ishibashi
Tomoko
T
Hara
Akira
A
Ohtsuka
Kunioki
K
Hayashi
D000818:Animals; D015220:Calcium Channels / Q000378:metabolism; D002122:Calcium Chloride / Q000737:chemistry / Q000493:pharmacokinetics*; D002132:Calcium Radioisotopes; D002478:Cells, Cultured; D002642:Chick Embryo; D003345:Corticosterone / Q000378:metabolism / Q000494:pharmacology*; D003402:Creatine Kinase / Q000378:metabolism; D008762:Methylhistidines / Q000378:metabolism; D009124:Muscle Proteins / Q000378:metabolism; D009210:Myofibrils / Q000187:drug effects* / Q000378:metabolism*; D009543:Nifedipine / Q000494:pharmacology; D014316:Tritium; D014443:Tyrosine / Q000378:metabolism
D015220:Calcium Channels; D002132:Calcium Radioisotopes; D008762:Methylhistidines; D009124:Muscle Proteins; D014316:Tritium; D014443:Tyrosine; D003402:Creatine Kinase; D009543:Nifedipine; D002122:Calcium Chloride; D003345:Corticosterone