Comparison of contractile properties between developing and regenerating soleus muscle: Influence of external calcium concentration upon the contractility

Abstract

In newborn rat skeletal extensor digitorum longus (EDL) muscle, it has been found that an influx of calcium from the extracellular medium is necessary for contraction, in contrast to the situation observed in adult EDL muscle. The aim of the present study was to determine the influence of the extracellular calcium concentration ([Ca]o) upon the contractile responses elicited in developing as well as in regenerating (notexin-injected) soleus (SOL) muscle. A morphological study was performed to follow the steps of postnatal development and regeneration in SOL muscle. In nominally calcium-free solution, the amplitudes of the twitch and tetanic tensions were greatly reduced in 1-14-day-old developing SOL muscles, as well as in notexin-injected SOL muscles. With longer times after birth, twitch and tetanic tensions of SOL muscle were less affected by the absence of calcium. This contrasts with notexin-injected SOL muscle in which the amplitudes of the contractions remained strongly dependent on [Ca]o. The present finding suggests that some functional characteristics are different in regenerating muscle fibers and may be of interest in the evaluation of the contractile properties of muscles in which injections of genetically engineered or not autologous myoblasts or viral vector have been performed.

Regulation of dihydropyridine receptor and ryanodine receptor gene expression in regenerating skeletal muscle

“…Expression of the cardiac isoform of the RyR was not observed. This is the first observation of this kind performed using regenerating skeletal muscle and this finding may contribute to the knowledge of the different mechanisms of EC coupling observed in regenerating versus normal adult skeletal muscle [30,31]. GAPDH expression has been used in the present study as an internal marker, as it is the gene most widely used for that purpose.…”

“…However, the mechanisms of EC coupling during skeletal muscle regeneration may be quite different from that in the normal adult. Functional studies have recently shown that, unlike that which is observed to occur in normal skeletal muscle, contraction of skeletal muscle injured by injection of notexin [30] or bupivacaine [31] is strongly dependent on extracellular calcium, as it is in developing skeletal muscle [13,16,39]. These observations suggest that regenerating skeletal muscle exhibits cardiac-like EC coupling.…”

Sodium withdrawal contractures in developing and regenerating rat extensor digitorum longus muscles

“…The preparation was then transferred to the experimental chamber and mounted in the way previously described. 15 Briefly, the two ends of the muscle were carefully snared by fine platinum wire loops, one fixed in the experimental bath and the other to the tip of a force transducer (displacement measuring system Kaman KD 2300, Colorado Spring, CO). Twitches were displayed on an oscilloscope (Tektronix 5115 N, Beaverton, OR) upon stimulation by current pulses (0.5 ms duration, twice the threshold value, frequency 0.07 Hz) applied between two platinum plate electrodes on each side of the channel.…”

“…External calcium dependence of the muscle contractility has been demonstrated in the early steps of postnatal development, 7,19 as well as during muscle regeneration, 15,16,18 in contrast to the situation observed in adult skeletal muscle. 8 In postnatal developing and regenerating muscles, neural control could be involved in the dependence of the contractility toward [Ca] o .…”

“…8 In postnatal developing and regenerating muscles, neural control could be involved in the dependence of the contractility toward [Ca] o . [15][16][17][18] Such an external calcium dependence of the contractility may also be encountered in long-term denervated extensor digitorum longus (EDL) muscles, 13 which also develop contractures when Na ions in the perfusing medium are replaced by tetraethylammonium chloride (TEACl) or lithium ions.…”