Membrane Responses of Frog Skeletal Muscle Fibers in Calcium‐Free Media

Effects of sulphydryl inhibitors on frog sartorius muscle: p‐chloromercuribenzoic acid and p‐chloromercuribenzenesulphonic acid

“…These same effects are also observed when the muscle is bathed in a calcium-free Ringer solution (Koketsu & Noda, 1962). Perhaps -SH group inhibition in the excitable membrane leads to a labilization of the membrane similar to that caused by the absence of external calcium.…”

On the role of calcium in the excitation‐contraction process of frog sartorius muscle

“…heart muscle (Weidmann, 1955), frog myelinated nerve fibres (Frankenhaeuser, 1957), lobster axon (Adelman & Adams, 1959) and squid axon (Frankenhaeuser & Hodgkin, 1957). The progressive decrease in amplitude of the action potential in frog sartorius fibres has also recently been observed by Koketsu & Noda (1962): it was furthermore found by them that the action potential, after being reduced in amplitude or completely lost by deprivation of calcium, is restored by anodal polarization of the fibre membrane, even after the preparation has been soaked in calcium-free solution containing EDTA for 24 hr. This is a very interesting finding in view of the fact, shown in the present work, that the decrease in amplitude of the action potential after removal of the extracellular calcium is not simply due to decrease of the resting potential.…”

The role of resting potential changes in the contractile failure of frog sartorius muscles during calcium deprivation

“…When sodium was present in the extracellular fluid, a spike was sometimes seen (cf. Koketsu & Noda, 1962), whether or not calcium was present. DISCUSSION Further confirmation has been obtained of the observation that calcium deprivation can lead to a drastic fall of membrane potential in frog skeletal muscle (Bulbring et al 1956;Ishiko & Sato, 1957;Edman & Grieve, 1961).…”

“…Frank (1958), using a paraffin-gap recording technique, reported that the depolarization produced by potassium chloride, and by implication the resting potential, was not affected by calcium depletion in the toe muscle of the frog. It is possible that the toe muscle is different in this respect to the frog sartorius muscle, in which the fall is now well documented (Bulbring et al 1956;Ishiko & Sato, 1957;Edman & Grieve, 1961;Koketsu & Noda, 1962); however, Curtis (1963) has also described a fall of resting potential in the toe muscle, using intracellular microelectrodes.…”

“…This suggests that the membrane potential at which inactivation occurs is higher in the absence of calcium. Inactivation of the sodium-carrying system of nerve occurs at a higher membrane potential when the calcium concentration is reduced (Frankenhaeuser, 1957;Frankenhaeuser & Hodgkin, 1957), and the loss of excitability which develops in calcium-free solutions may be reversed by anodal polarization, both in nerve (Woronzow, 1924) and in muscle (Koketsu & Noda, 1962). There are no reports in the literature regarding the influence of calcium on the membrane potential at which inactivation of the excitation-contraction coupling system occurs.…”