TY - JOUR

T1 - Contraction-induced increases in Na+-K+-ATPase mRNA levels in human skeletal muscle are not amplified by activation of additional muscle mass

AU - Nordsborg, Nikolai

AU - Thomassen, Martin

AU - Lundby, Carsten

AU - Pilegaard, Henriette

AU - Bangsbo, Jens

N1 - PUF 2005 5200 009

PY - 2005

Y1 - 2005

N2 - The present study tested the hypothesis that exercise with a large compared with a small active muscle mass results in a higher contraction-induced increase in Na+-K+-ATPase mRNA expression due to greater hormonal responses. Furthermore, the relative abundance of Na+-K+-ATPase subunit a1, a2, a3, a4, ß1, ß2, and ß3 mRNA in human skeletal muscle was investigated. On two occasions, eight subjects performed one-legged knee extension exercise (L) or combined one-legged knee extension and bilateral arm cranking (AL) for 5.00, 4.25, 3.50, 2.75, and 2.00 min separated by 3 min of rest. Leg exercise power output was the same in AL and L, but heart rate at the end of each exercise interval was higher in AL compared with L. One minute after exercise, arm venous blood lactate was higher in AL than in L. A higher level of blood epinephrine and norepinephrine was evident 3 min after exercise in AL compared with L. Nevertheless, none of the exercise-induced increases in a1, a2, ß1, and ß3 mRNA expression levels were higher in AL compared with L. The most abundant Na+-K+-ATPase subunit at the mRNA level was ß1, which was expressed 3.4 times than a2. Expression of a1, ß2, and ß3 was less than 5% of the a2 expression, and no reliable detection of a3 and a4 was possible. In conclusion, activation of additional muscle mass does not result in a higher exercise-induced increase in Na+-K+-ATPase subunit-specific mRNA.

AB - The present study tested the hypothesis that exercise with a large compared with a small active muscle mass results in a higher contraction-induced increase in Na+-K+-ATPase mRNA expression due to greater hormonal responses. Furthermore, the relative abundance of Na+-K+-ATPase subunit a1, a2, a3, a4, ß1, ß2, and ß3 mRNA in human skeletal muscle was investigated. On two occasions, eight subjects performed one-legged knee extension exercise (L) or combined one-legged knee extension and bilateral arm cranking (AL) for 5.00, 4.25, 3.50, 2.75, and 2.00 min separated by 3 min of rest. Leg exercise power output was the same in AL and L, but heart rate at the end of each exercise interval was higher in AL compared with L. One minute after exercise, arm venous blood lactate was higher in AL than in L. A higher level of blood epinephrine and norepinephrine was evident 3 min after exercise in AL compared with L. Nevertheless, none of the exercise-induced increases in a1, a2, ß1, and ß3 mRNA expression levels were higher in AL compared with L. The most abundant Na+-K+-ATPase subunit at the mRNA level was ß1, which was expressed 3.4 times than a2. Expression of a1, ß2, and ß3 was less than 5% of the a2 expression, and no reliable detection of a3 and a4 was possible. In conclusion, activation of additional muscle mass does not result in a higher exercise-induced increase in Na+-K+-ATPase subunit-specific mRNA.

U2 - 10.1152/ajpregu.00771.2004

DO - 10.1152/ajpregu.00771.2004

M3 - Journal article

C2 - 15705803

VL - 289

SP - R84-R91

JO - American Journal of Physiology

JF - American Journal of Physiology

SN - 0363-6119

IS - 1

ER -