L-thyroxine activates the intracellular Ca2+ release channel of skeletal muscle sarcoplasmic reticulum.
L-thyroxine activated the Ca2+ release channel (ryanodine receptor) of skeletal muscle. [3H]ryanodine binding was stimulated by L-thyroxine in a dose dependent manner producing a two-fold increase at 250 microM. The same concentration induced a release of approximately 40% of the 45Ca2+ passively loaded into sarcoplasmic reticulum in 100 msec. Ca2+ release channel activity monitored in planar bilayers increased in the presence of 250 microM L-thyroxine from a control open probability of 0.02 +/- 0.03 to 0.17 +/- 0.12. Thyroid hormones may directly open Ca2+ release channels of skeletal muscle, thus altering intracellular Ca2+ homeostasis.
Department of Anesthesiology, University of Wisconsin Medical School, Madison 53706.
T J
TJ
Connelly
R
R
el-Hayek
M
M
Sukhareva
R
R
Coronado
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D008051:Lipid Bilayers; D008564:Membrane Potentials / Q000187:drug effects; D009124:Muscle Proteins / Q000187:drug effects / Q000502:physiology*; D009132:Muscles / Q000378:metabolism*; D012433:Ryanodine / Q000378:metabolism; D019837:Ryanodine Receptor Calcium Release Channel; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*; D013552:Swine; D013974:Thyroxine / Q000494:pharmacology*
D015220:Calcium Channels; D008051:Lipid Bilayers; D009124:Muscle Proteins; D019837:Ryanodine Receptor Calcium Release Channel; D012433:Ryanodine; D013974:Thyroxine; D002118:Calcium