Abstract
In loose patch clamp experiments on intact sartorius muscle fibers of the frog Rana temporaria, there have been two types of waveforms of extracellularly recorded action potentials (AP). Responses of the first type (T1AP) consisted of an initial positive phase with a subsequent phase of strong negativity, the latter only in a few cases followed by a weak positive phase. Responses of the second type (T2AP) always had an additional positive phase concluding their waveform. In the detubulated fibers, only T1AP were recorded. Application of Ba2+ (10 μM) to the muscle led to a significant increase in the amplitude of the third T2AP phase whereas the T1AP characteristics of both intact and detubulated muscle preparations remained unchanged. In some of the studied intact fibers, after Ba2+ or ouabain (50 μM) applied, the latest positive signal phase was replaced by a negative phase. The amplitude of this latest negative phase was increased markedly by highfrequency stimulation. Under the simultaneous action of ouabain and Ba2+, there was a summation of their effects. Our results can be tentatively explained by that the T-system of a muscle fiber produces electrical responses substantially differing in their pattern and barium sensitivity from those transmitted across cell membranes. These differences could be resultant from the activity of T-tubular inwardly rectifying potassium channels (Kir) and that of Na,K-ATPase as they both provide absorption of excessive extracellular potassium.
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Original Russian Text © I.V. Kubasov, M.G. Dobretsov, 2012, published in Zhurnal Evolyutsionnoi Biokhimii i Fiziologii, 2012, Vol. 48, No. 4, pp. 360–366.
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Kubasov, I.V., Dobretsov, M.G. Effects of barium and ouabain on electrogenesis in various sites of intact and detubulated skeletal muscle fibers of the frog R. temporaria . J Evol Biochem Phys 48, 422–429 (2012). https://doi.org/10.1134/S0022093012040068
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DOI: https://doi.org/10.1134/S0022093012040068