The effect of nitrate on the active state of muscle

Abstract

The inherent response of the contractile material of muscle to a stimulus, the active state, is abrupt and reaches its full extent immediately at the end of the latent period; at this time the contractile material is capable of exerting the same tension in response to a single stimulus as it does in a tetanus (Hill, 1949).But the development of tension by whole muscle in an isometric contraction is gradual, because there is a series elastic component which must be stretched while tension is being developed and the rate of this stretching is limited by the relation between force and velocity of shortening ofthe contractile material.For a tetanus, where the successive elements of the stimulus maintain the active state at its full extent for the period of stimulation, Hill (1949) has shown that the form of the isometric myogram depends only on the stress-strain relation of the series elasticity and on the characteristic relation between force and velocity of shortening. In a single maximal twitch a third factor is involved, for the active state begins to decay very soon after it has been established

Calcium Influx in Skeletal Muscle at Rest, During Activity, and During Potassium Contracture

“…The increased entry of calcium in nitrate solution could also account for the greater twitch and the prolonged contractile active state. Thus, the prolonged active state, to which is attributed the greater twitches (25), could be a consequence of a greater "slug" of entering calcium that requires more time to be ejected or bound by intracellular binding sites (of. reference 8).…”

“…It will soon be shown that 60 minutes is too long because of the latter; also, that 10 minutes is not so short as to limit fiber entry appreciably by virtue of incomplete diffusion in the extracelluiar space--already noted by Harris in his studies of anion penetration (10). Second, before the tissues were dried and ashed for counting, the Ca 4~ in the extracellular water and on the superficial binding sites of the surface of the fibers and in the connective tissue was removed routinely by soaking the individual muscles at frequent intervals (5,10,25, and 50 minutes) in a series of radioisotope-free Ringer's, each of 5 ml., for a total of 90 minutes. This removes most of the extraneous Ca 45 (34), which would have obscured the changes in the Ca 46 content of the myoplasm.…”

Active State of Muscle in Iodoacetate Rigor

“…The variations in rate of redevelopment of tension following release are of interest since, as in the comparably treated normal muscle (12,21), this rate at any moment may be taken as a measure of the concurrent intensity of the rigor active state. We limit ourselves to considerations of this rate during the foot of the original rise of rigor and at onset of its redevelopment following each quick release, this rate being indicated by the corresponding slopes of the various tension-time curves given in the records of Fig.…”

Effect of SCN on Potassium Contracture in Twitch Muscle Fibers of the Frog

“…As mentioned previously, it seems that the T-membrane and/or triadic junction of twitch fibers are the sites for the potentiating action of SCN on K-contracture tension as well as those on twitch tension. It has been generally accepted that the potentiation of twitch tension by anomalous anions is due to a prolongation of the active state of contractile elements caused by lengthening the duration of the mechanically effective period (HILL and MACPHERSON, 1954;RITCHIE, 1954;SANDOW, 1965). On the other hand, K-contracture is induced by a maintained membrane depolarization which is past the mechanical threshold (HODGKIN and HoROwICZ, 1960a), thus it may be considered that the mechanically effective period during K-contracture is lengthened enough.…”