Effects of anions and cations on the resting membrane potential of internally perfused barnacle muscle fibres

Murayama

1975

J. Membrain Biol.

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The resting membrane potential data existing in the literature for the giant axon of the squid, frog muscle and barnacle muscle have been analyzed from the standpoint of the theory of membrane potential due to Kobatake and co-workers. The average values derived for the effective charge density phi chi (where phi is a constant, 0 less than phi less than 1, and represents the fraction of counterions that are free, and chi is the stoichiometric charge density in the membrane) present on the different biomembranes existing in their normal ionic environment are 0.3, 0.325 and 0.17 M for the squid axon, frog and barnacle muscles, respectively. On the assumption that the values of phi are 0.4 and 0.2 for nerve and muscle membranes, respectively, values of 0.75, 1.62 and 0.85 M have been derived for the stoichiometric charge density (chi) present in the respective biological membranes. These correspond to 1 negative charge per 222, 103 and 195 A2 of the membrane area of the squid axon, frog and barnacle muscles, respectively.

Section: Discussionmentioning

confidence: 98%

Estimation of surface charges in some biological membranes

Murayama

1975

J. Membrain Biol.

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“…Keynes, Rojas, Taylor and Vergara (1973) have been successful in perfusing the giant barnacle muscle fiber internally with isotonic solutions of K aspartate. Following this, Lakshminarayanaiah and Rojas (1973) were able to manipulate the internal and external environments of the barnacle muscle cell using a variety of salt solutions whose ionic strength was varied over a wide range. The tonicity of the solutions was maintained with sucrose.…”

mentioning

confidence: 99%

Potentiometric estimation of charges in barnacle muscle fibers under internal perfusion

1974

J. Membrain Biol.

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Single barnacle muscle fibers from Megabalanus Psittacus (Darwin) were internally perfused with a number of solutions of K-acetate of concentration 6"2 which was increased from 100 to 600 mM maintaining a pH of 7.5. The external solutions at the same pH contained 40 mM MgAc 2 and K-acetate of concentration C1 which was varied from 10 through 60 mM. The tonicity of both internal and external fluids was maintained at 1,000 mosmole with sucrose. The membrane potential E m (the potential was referred to the external solution as ground) arising across the fiber membrane was measured using those internal and external solutions which maintained the ratio (C2/C1) at 10. Similar measurements but now maintaining the ratio (C2/C~) at 2, where C~ was the concentration of Tris-C1 in the internal perfusion fluid and was increased from 100 to 250 mM and C2 was the concentration of total C1 in the external fluid which contained 40 mM MgC12 and different amounts of Tris-C1 (120 to 420 raM), were also made using various isotonic solutions at pH 4.0. The measured values of E m corrected for the liquid junction potentials, on interpolation with the theoretical curves of E m plotted against log (1/C1) derived from the theory of membrane potential developed by Teorell and by Meyer and Sievers, gave values of 0.019 and 0.7 M for the density of fixed charges present on the membrane at pH 7.5 (cation selective) and 4.0 (anion selective), respectively. Also, values of 2.3 at pH 7.5 and 1.0 at pH 4.0 were derived for the mobility ratio of cation to anion.It is well recognized that charges present on the surface of biological membranes influence various aspects of biological behavior. A surface charge model has been used by Gilbert and Ehrenstein (1969) to explain some of the voltage-dependent characteristics of the conductance of the nerve fiber. Other biological phenomena, e.g. muscle contraction, protoplasmic streaming, etc., are likely to be greatly influenced by the nature of the charged membrane surfaces. Consequently, a number of techniques, mostly electrokinetic in nature, have been utilized by a number of investigators (see Gilbert, 1971 for a brief review) to estimate the density of charges present in membranes of various biological preparations. Recently,

“…Consequently, it should arise by the outward movement of positive charge, probably residual K, whose outward movement is not suppressed by TEA. The possibility that TEA itself might move is unlikely in view of the high selectivity of the membrane to K over TEA (Lakshminarayanaiah & Rojas, 1973).…”

Section: Resultsmentioning

confidence: 99%

Calcium carrying system in the giant muscle fibre of the barnacle species, Balanus nubilus

Beirão

The Journal of Physiology

1979

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SUMMARY1. Single barnacle muscle fibres from Balanus nubilus were internally perfused with an isotonic solution containing 180 mM-tetraethylammonium acetate and the effects of Ca concentration in the external solution on the voltage-clamp currents, especially the initial inward current, were examined.2. Muscle fibre in external solution containing no added Ca (concentration of Ca < 10-5 M) gave a current-voltage curve that showed a small inward current followed by a small outward current. An identical curve was obtained when the chloride in the external solution was replaced by acetate.3. The peak inward current increased with increase in Ca concentration in the external solution; but the increase in peak current for equal increments of Ca concentration was reduced and attained saturation conforming to an adsorption regime which can be described by the Langmuir equation.4. A double reciprocal plot of peak inward current due to Ca as a function of Ca concentration gave values of 20-7 mm and 200 % (the current due to 20 mm-Ca normalized to 100 %) for the dissociation constant and the maximum current respectively. These values were found to depend on the concentration of Mg used in the external solutions. 5. The peak inward Ca currents measured at two Ca concentrations as a function of pH were unaffected in the pH range 6-5-8-8; however when the pH was reduced below 6-5, the currents were depressed.