Effect of Na ⁺ ,K ⁺ -ATPase inhibition during salbutamol exposure on subcellular compartmentalized glycogen metabolism. (A, C, and E) Single-fiber values of glycogen in three distinct subcellular pools: intermyofibrillar, intramyofibrillar, and subsarcolemmal. Data are shown as box plots displaying the first and third quartiles and split by the median. n = 32–45 fibers from 11 to 16 muscles. (B, D, and F) Point estimates with 95% confidence interval from linear mixed effect model on square root–transformed data from (intermyofibrillar and intramyofibrillar glycogen) or log-transformed data (subsarcolemmal glycogen) from A. (G) Illustrations of the spatial association between Na⁺,K⁺ ATPases situated at the t-tubular membrane (orange) and intramyofibrillar glycogen. (H) Muscle homogenate glycogen concentration shown as mean with 95% confidence interval. n = 11–16 muscles. (I) Muscle homogenate lactate concentration shown as mean with 95% confidence interval. n = 11–16 muscles. Interaction or main effects were tested using linear mixed effect model on square root–transformed (intermyofibrillar and intramyofibrillar glycogen in A and C, respectively), log-transformed (subsarcolemmal glycogen in E), or nontransformed data (H and I) with salbutamol and ouabain as fixed effects and rat as random effect. P values for two-way interactions were 0.164, 0.010, 0.225, 0.281, and 0.052 for intermyofibrillar, intramyofibrillar, subsarcolemmal glycogen, homogenate glycogen, and homogenate lactate, respectively.