Schwaller, B. Dick, J. Dhoot, G. Carroll, S. Vrbova, G. Nicotera, P. Pette, D. Wyss, A. Bluethmann, H. Hunziker, W. Celio, M. R. <jats:p> The calcium-binding protein parvalbumin (PV) occurs at high concentrations in fast-contracting vertebrate muscle fibers. Its putative role in facilitating the rapid relaxation of mammalian fast-twitch muscle fibers by acting as a temporary buffer for Ca<jats:sup>2+</jats:sup> is still controversial. We generated knockout mice for PV (PV −/−) and compared the Ca<jats:sup>2+</jats:sup> transients and the dynamics of contraction of their muscles with those from heterozygous (PV +/−) and wild-type (WT) mice. In the muscles of PV-deficient mice, the decay of intracellular Ca<jats:sup>2+</jats:sup> concentration ([Ca<jats:sup>2+</jats:sup>]<jats:sub>i</jats:sub>) after 20-ms stimulation was slower compared with WT mice and led to a prolongation of the time required to attain peak twitch tension and to an extension of the half-relaxation time. The integral [Ca<jats:sup>2+</jats:sup>]<jats:sub>i</jats:sub>in muscle fibers of PV −/− mice was higher and consequently the force generated during a single twitch was ∼40% greater than in PV +/− and WT animals. Acceleration of the contraction-relaxation cycle of fast-twitch muscle fibers by PV may confer an advantage in the performance of rapid, phasic movements. </jats:p> https://sonar.ch/global/documents/139500 eng info:eu-repo/semantics/altIdentifier/doi/10.1152/ajpcell.1999.276.2.c395 info:eu-repo/semantics/altIdentifier/issn/0363-6143 American Journal of Physiology-Cell Physiology. - American Physiological Society. - 1999, vol. 276, no. 2, p. C395-C403 Cell Biology Physiology Prolonged contraction-relaxation cycle of fast-twitch muscles in parvalbumin knockout mice http://purl.org/coar/resource_type/c_6501