Na⁺-K⁺ pump location and translocation during muscle contraction  in rat skeletal muscle

TY - JOUR

T1 - Na+-K+ pump location and translocation during muscle contraction  in rat skeletal muscle

AU - Kristensen, Michael

AU - Rasmussen, Martin Krøyer

AU - Juel, Carsten

N1 - Na+–K+ pump translocation - Caveolae - Caveolin-3 - Intracellular pool - Acute exercise

PY - 2008

Y1 - 2008

N2 - Muscle contraction may up-regulate the number of Na+-K+ pumps in the plasma membrane by translocation of subunits. Since there is still controversy about where this translocation takes place from and if it takes place at all, the present study used different techniques to characterize the translocation. Electrical stimulation and biotin labeling of rat muscle revealed a 40% and 18% increase in the amounts of the Na+-K+ pump a2 subunit and caveolin-3 (Cav-3), respectively, in the sarcolemma. Exercise induced a 36% and 19% increase in the relative amounts of the a2 subunit and Cav-3, respectively, in an outer-membrane-enriched fraction and a 41% and 17% increase, respectively, in sarcolemma giant vesicles. The Na+-K+ pump activity measured with the 3-O-MFPase assay was increased by 37% in giant vesicles from exercised rats. Immunoprecipitation with Cav-3 antibody showed that 17%, 11% and 14% of the a1 subunits were associated with Cav-3 in soleus, extensor digitorum longus, and mixed muscles, respectively. For the a2, the corresponding values were 17%, 5% and 16%. In conclusion; muscle contraction induces translocation of the a subunits, which is suggested to be caused partly by structural changes in caveolae and partly by translocation from an intracellular pool.

AB - Muscle contraction may up-regulate the number of Na+-K+ pumps in the plasma membrane by translocation of subunits. Since there is still controversy about where this translocation takes place from and if it takes place at all, the present study used different techniques to characterize the translocation. Electrical stimulation and biotin labeling of rat muscle revealed a 40% and 18% increase in the amounts of the Na+-K+ pump a2 subunit and caveolin-3 (Cav-3), respectively, in the sarcolemma. Exercise induced a 36% and 19% increase in the relative amounts of the a2 subunit and Cav-3, respectively, in an outer-membrane-enriched fraction and a 41% and 17% increase, respectively, in sarcolemma giant vesicles. The Na+-K+ pump activity measured with the 3-O-MFPase assay was increased by 37% in giant vesicles from exercised rats. Immunoprecipitation with Cav-3 antibody showed that 17%, 11% and 14% of the a1 subunits were associated with Cav-3 in soleus, extensor digitorum longus, and mixed muscles, respectively. For the a2, the corresponding values were 17%, 5% and 16%. In conclusion; muscle contraction induces translocation of the a subunits, which is suggested to be caused partly by structural changes in caveolae and partly by translocation from an intracellular pool.

KW - Faculty of Science

U2 - 10.1007/s00424-008-0449-x

DO - 10.1007/s00424-008-0449-x

M3 - Journal article

C2 - 18214523

SN - 0031-6768

VL - 456

SP - 979

EP - 989

JO - Pflügers Archiv: European Journal of Physiology

JF - Pflügers Archiv: European Journal of Physiology

IS - 5

ER -