Parvalbumin content and Ca2+ and Mg2+ dissociation rates correlated with changes in relaxation rate of frog muscle fibres.

Abstract

SUMMARY1. Experiments were done to test the hypothesis that parvalbumin (PA) promotes relaxation in frog skeletal muscle. Single fibres and purified PA from Rana temporaria skeletal muscle were used to determine the relationship between PA concentration ([PA]), Ca2" and Mg2" dissociation rates from PA and changes in rate of relaxation as a function of tetanus duration at 0°C. 3. Relaxation rate from an isometric tetanus slows progressively as a function of tetanus duration with an exponential time course and a rate constant of 1P18 + 0 35 s-' (n = 17). Time course of recovery of relaxation rate after a prolonged tetanus is exponential with a rate constant of 0O12 + 0-02 s-1 (n = 14).4. The extent of recovery of relaxation rate after a prolonged tetanus was correlated with total [PA] in fibres (correlation coefficient (r) = 0-80, n = 7; P < 005).5. Dissociation rate constants for Mg2+ and Ca2+ from purified PA are 0-93+0-02 s-' (n = 5) and 0 19+0-01 s-' (n = 5), respectively. Dissociation rate constants were not significantly different for PA isoforms IVa and IVb. These rate constants are similar to the rate constants determined for the time courses of slowing and recovery of relaxation rate, respectively. 6. Results suggest that the time courses of slowing and recovery of relaxation rate may be controlled, to a large extent, by Mg2+ and Ca2+ dissociation from PA, respectively. This evidence supports a role for PA in facilitating relaxation during a tetanus in frog skeletal muscle at 0 'C.

Differences in locomotor performance between individuals: importance of parvalbumin, calcium handling and metabolism

“…The increased expression of parv2 in our zebrafish indicates that fast-twitch muscles and sprint performance are more sensitive to changes in parvalbumin concentration. This conclusion is supported by the preferential, albeit not exclusive, expression of parvalbumin in fast twitch, white muscle fibres (Hou et al, 1991;Schoenman et al, 2010). We have identified a number of molecular traits that can explain differences in sprint and sustained locomotor performance between individuals.…”

Resurrecting prehistoric parvalbumins to explore the evolution of thermal compensation in extant Antarctic fish parvalbumins

“…In addition to the steady-state Ca 2+ K d data, we determined the unidirectional rate constants of Ca 2+ binding and dissociation. These two rate constants define the interaction of Ca 2+ with PV and it has been shown that these parameters can directly affect muscle function (Hou et al, 1991;Hou et al, 1992). The equilibrium Ca 2+ -binding constant K d is determined by the ratio of off-rate over on-rate (K d k off /k on ).…”

“…Off-rates for Ca 2+ were measured using terbium fluorescence as a reporter ligand based on established methods (Hou et al, 1991;Hou et al, 1992). PV has a higher affinity for terbium and the off-rate of Ca 2+ can be measured as it is replaced by terbium and terbium fluorescence increases.…”

Parvalbumin correlates with relaxation rate in the swimming muscle of sheepshead and kingfish

“…The dissociation rate for Mg 2+ is thought to determine the physiological properties of parvalbumin and determine its contribution to relaxation rate, particularly in sub-maximal tetanic contractions (Hou et al, 1991(Hou et al, , 1993. Dissociation rates of Mg 2+ from parvalbumin might vary between isoforms of parvalbumin.…”

“…The amount of parvalbumin present in a given muscle will affect relaxation. Greater parvalbumin content is typically associated with fast-twitch muscle of various vertebrates -muscle with relatively high rates of relaxation (Heizmann et al, 1982;Hou et al, 1991;Berchtold et al, 2000).…”