Key result
A conditioning stimulus increased mean concentric force in wildtype and skMLCK -/- mouse muscles to 1.31-1.35 and 1.19-1.21 of pre-stimulus levels, respectively (p<0.05).
p-value: p=< 0.05
Concentric force potentiation is inversely related to unpotentiated force in both WT and skMLCK -/- mouse skeletal muscles, suggesting crossbridge attachment influences potentiation magnitude independently of myosin phosphorylation.
Mouse muscle findings warrant no clinical translation yet; leaves open skMLCK-independent crossbridge mechanisms for mechanistic studies.
The isometric potentiation associated with myosin phosphorylation is force dependent. The purpose of this study was to assess the influence of a pre‐existing period of isometric force on the concentric force potentiation displayed by mouse muscles with and without the ability to phosphorylate myosin. We tested isometric (ISO) and concentric (CON) potentiation, as well as concentric potentiation after isometric force (ISO‐CON), in muscles from wildtype (WT) and skeletal myosin light chain kinase deficient (skMLCK ‐/‐ ) mice. A conditioning stimulus increased (i.e. potentiated) mean concentric force in the ISO‐CON and CON conditions to 1.31±0.02 and 1.35±0.02 (WT) and to 1.19±0.02 and 1.21±0.01 (skMLCK ‐/‐ ) of pre‐stimulus levels, respectively (data n = 6‐8, p < 0.05). No potentiation of mean isometric force was observed in either genotype. The potentiation of mean concentric force was inversely related to relative tetanic force level (P/P o ) in both genotypes. Moreover, concentric potentiation varied greatly within each contraction type and was negatively correlated with unpotentiated force in both genotypes. Thus, although no effect of pre‐existing force was observed, strong and inverse relationships between concentric force potentiation and unpotentiated concentric force may suggest an influence of attached and force generating crossbridges on potentiation magnitude in both WT and skMLCK ‐/‐ muscles.
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Gittings et al. (2015) studied Mouse skeletal muscle function. Conditioning stimulus vs. Pre-stimulus levels was evaluated on Mean concentric force potentiation (p=< 0.05). A conditioning stimulus increased mean concentric force in wildtype and skMLCK -/- mouse muscles to 1.31-1.35 and 1.19-1.21 of pre-stimulus levels, respectively (p<0.05).
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