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

Abstract

Nordsborg, Nikolai, Martin Thomassen, Carsten Lundby, Henriette Pilegaard, and Jens Bangsbo. Contraction-induced increases in Na ϩ -K ϩ -ATPase mRNA levels in human skeletal muscle are not amplified by activation of additional muscle mass.

Interspersed normoxia during live high, train low interventions reverses an early reduction in muscle Na+, K+ATPase activity in well-trained athletes

“…Athletes continue their normal heavy exercise training in normoxia during daytime hours, whilst they are exposed to nightly hypoxia in LHTL. Acute exercise of only a few minutes duration can upregulate Na + , K + ATPase mRNA (Murphy et al 2004Nordsborg et al 2005) whilst just 6 days of training (Green et al 1993 and chronic training upregulated Na + , K + ATPase content (McKenna et al 1993;Green et al 1999a). As athletes in this study maintained~15 h week -1 of training, it is therefore possible that a potentially larger hypoxiainduced decrease in Na + , K + ATPase activity was attenuated by the upregulatory impact of daily, ongoing, heavy training.…”

“…It is possible that a large decrease in Na + , K + ATPase activity had occurred early in the 23-n period, but was followed by a compensatory increase. This could in part be consequential to the ongoing, heavy daily training common to well-trained athletes (Hawley et al 1997), as exercise provides a strong stimulatory effect on muscle Na + , K + ATPase gene expression (Murphy et al 2004Nordsborg et al 2005) and training increases Na + , K + ATPase content (Green et al 1993McKenna et al 1993;Madsen et al 1994;Evertsen et al 1997;Medbø et al 2001). An early depressive response would be consistent with the much larger decline in muscle Na + , K + ATPase activity during exercise in acute hypoxia .…”

Reduced volume but increased training intensity elevates muscle Na+-K+ pump α1-subunit and NHE1 expression as well as short-term work capacity in humans

“…†Significant difference (P Ͻ 0.05) from the level of glycogen post-EX1. subunits in muscle (23,32), and it may be that, in the present study, the amount of these isoforms was already high in the subjects before the sprint training, since endurance training has been shown to increase the Na ϩ -K ϩ pump ␣ 2 -and ␤ 1 -isoform protein expression (17). Likewise, in two studies of sedentary people performing repeated high-intensity training, elevated levels of the ␣ 2 -and ␤ 1 -subunits were found (29,31), but in only one of the studies the level of the ␣ 1 -subunit was higher after training (31).…”

Dissociation between changes in muscle Na+-K+-ATPase isoform abundance and activity with consecutive days of exercise and recovery

“…During the training protocol V max was observed to decline, a finding that could be attributed to failure of the enzyme to recover from the inhibiting effects of the previous exercise bout. More recent studies report the potency of a single exercise session for increasing transcription potential as evidenced by the increases that occur soon after the exercise in a variety of ␣-and ␤-mRNA isoform transcripts (32,33,35,39). Prolonged submaximal cycling exercise, as an example, resulted in increases in the respective mRNAs for ␣ 1 , ␣ 3 , and ␤ 2 but not the mRNAs for ␣ 2 , ␤ 1 , and ␤ 3 , all peaking at variable time points within the first 24 h following exercise (32).…”