Submitted on August 25, 2003
Accepted on March 10, 2004
EFFECT OF ENDURANCE-EXERCISE ON THE Ca2+-PUMPS FROM TRANSVERSE TUBULE AND SARCOPLASMIC RETICULUM OF RABBIT SKELETAL MUSCLE
Viola Becker1, Hugo Gonzalez-Serratos2, Rocio Alvarez3, Michael Baermann4, Claudine Irles5, and Alicia Ortega1*
1 Biochemistry, Universidad Nacional Autonoma de Mexico, Mexico, D.F., Mexico; Biochemistry, Instituto Nacional de Perinatologia, Mexico, D.F., Mexico
2 Physiology, University of Maryland, Baltimore, Maryland, USA
3 Biochemistry, Universidad Nacional Autonoma de Mexico, Mexico, D.F., Mexico
4 Physics (Biophysics), Technical University of Munich, Garching, Bayern, Germany
5 Biochemistry, Instituto Nacional de Perinatologia, Mexico, D.F., Mexico
* To whom correspondence should be addressed. E-mail: cirles{at}pasteur.fr.
The sarcoplasmic reticulum (SR) Ca2+-pump is the main homeostatic regulatory mechanism in fast skeletal muscle that maintains cytosolic Ca2+ concentration ([Ca2+]i) at the nM level at rest. The transverse tubule (TT) Ca2+-pump transports cytosolic Ca2+ to the extracellular space. During prolonged muscular activity [Ca2+]i may increase. TT and SR isolated microsomal vesicles were highly purified and checked the purity by immunoblotting. The present study shows the effects of endurance-exercise on the activities and structures of the TT and SR Ca2+-pumps of fast skeletal muscle from rabbit at rest. The Ca2+-pump activity increased manifolds in TT but did not change in SR. The protein denaturalization profiles obtained by differential scanning calorimetry showed: a) a shift in the transition temperature (Tm) and an increase in the enthalpy of the TT Ca2+-pump, and b) a significant change in the Tm of the SR Ca2+-pump Ca2+-binding domain. We conclude that the TT Ca2+-pump activity was upgraded in association with structural changes, in order to handle the changes in [Ca2+]i and TT lumen [Ca2+] that occur during endurance-exercise.
