The Journal of Membrane Biology

Klingenberg, M.

doi: 10.1007/BF01875961pmid: 7003152

Lassalles, Jean-Paul; Hartmann, Anne; Theillier, Michel

doi: 10.1007/BF01875962pmid: 6969315

When a frog skin is used to separate two compartments, and lithium is added to the external medium, transmembrane electric potential oscillations frequently occur. When no external current is imposed, sustained oscillations, with a period of about 10 min, are maintained for several hours. An oscillation of the Na+ influx accompanies the electric oscillation, though the two oscillations are out of phase to a greater or less extent.

Chiu, Vincent; Mouring, Donald; Watson, Brant; Haynes, Duncan

doi: 10.1007/BF01875963pmid: 7441722

The binding of the anionic fluorescent probe 1-anilino-8-naphthalene-sulfonate (ANS−) was used to estimate the surface potential of fragmented sarcoplasmic reticulum (SR) derived from rabbit skeletal muscle. The method is based on the observation that ANS− is an obligatory anion whose equilibrium constant for binding membranes is proportional to the electrostatic function of membrane surface potential, exp(eΨ0/kT, where Ψ0 is the membrane surface potential,e is the electronic charge, andkT has its usual meaning. The potential measured is characteristic of the ANS− bindings of phosphatidylcholine head groups and is about one-third as large as the average surface potential predicted by the Gouy-Chapman theory. At physiological ionic strength the surface potentials, measured by ANS−, referred to as the aqueous phase bathing the surface, were in the range −10 to −15 mV. This was observed for the outside and inside surfaces of the Ca2+-ATPase-rich fraction of theSR and for both surfaces of theSR fraction rich in acidic Ca2+ binding proteins. The inside and outside surfaces were differentiated on the basis of ANS− binding kinetics observed in stopped-flow rapid mixing experiments. A mechanism by which changes in Ca2+ concentration could give rise to an electrostatic potential across the membrane and possibly result in changes in Ca2+ permeability.

Epstein, Nava; Hess, George; Kim, Peter; Noble, Richard

doi: 10.1007/BF01875964pmid: 7441723

The inactivation (desensitization) of the acetylcholine receptor by carbanylcholine, a stable analogue of acetylcholine, has been investigated in eel Ringer's solution, pH 7.0, 0°C, by measurements of (i) ion flux and (ii) the kinetics of the reaction of [125I]-α-bungarotoxin with the receptor. The effect of preincubation with carbamylcholine is significantly different in the two types of measurement. In both the receptor-controlled flux of inorganic ions and the toxin-binding kinetics a biphasic process has been observed (Hess, G.P., Lipkowitz, S., Struve, G.E., 1978,Proc. Nat. Acad. Sci. USA 75:1703; Hess, G.P. et al., 1975,Biochem. Biophys. Res. Commun. 64: 1018; Bulger, J.E. et al., 1977,Biochemistry 16: 684), only the initial fast phase of which is inhibited and the subsequent slow phase persists. However, preincubation with carbamylcholineper se has no effect on the toxin reaction. The results obtained are consistent with the proposal of Katz and Thesleff (Katz, B., Thesleff, S., 1957,J. Physiol. (London) 138: 65) that the active form of the receptor is converted to an inactive form in the presence of acetylcholine receptor ligands, and with our previous experiments (Hess et al., 1978) which indicated that one receptor form is responsible for the initial fast phase of both the receptor-controlled ion flux and the toxin binding reaction, and that its conversion to the other form results in the slow phases in these two measurements.

Ehrenfeld, J.; Garcia-Romeu, F.

doi: 10.1007/BF01875965pmid: 6969316

Sodium and chloride influxes across the nonshort-circuited isolated skin ofRana esculenta were measured at widely varying external ionic concentrations.

Benos, D.; Mandel, L.; Simon, S.

doi: 10.1007/BF01875966pmid: 6969317

Previously we have shown that the inhibition of active transport by amiloride is noncompetitive with sodium inRana catesbeiana skin, suggesting that amiloride acts at a site separate from the sodium entry site (Benos, D.J., Mandel, L.J., Balaban, R.S. 1979,J. Gen Physiol. 73: 307). In the present study, the effects of a number of sulfhydryl, amino, and carboxyl group selective reagents were studied on short-circuit current (I sc) as well as the efficacy of amiloride in bullfrog skin, to determine those functional ligands which may be involved with either of these processes.

Kometani, Tadaatsu; Kasai, Michiki

doi: 10.1007/BF01875967pmid: 7441724

The volume change of sarcoplasmic reticulum vesicles was induced by Ca2+ uptake. This volume change was measured by the light-scattering method. When vesicles were shrunk beforehand under the condition that anions are more permeable than cations, they swelled during Ca2+ uptake due to the concomitant incorporation of anions. On the contrary, they shrank with Ca2+ uptake due to the extrusion of cations under the condition that cations are more permeable than anions. From the analysis of the volume change it was concluded that all ions other than Ca2+ were transported passively in order to neutralize the membrane potential generated by the Ca2+ pump. These results support the idea that the Ca2+ pump is electrogenic. By using this technique, it became possible to measure the fast Ca2+ uptake rate. The dependence of the Ca2+ uptake rate on the Ca2+ concentration suggests that the site at which Ca2+ inhibits Ca2+ uptake is located inside the vesicle. From the osmotic response of the vesicles, the intravesicular concentration of free Ca2+ was estimated to be about 15mm, when Ca2+ was fully taken up under the physiological condition.

Ottina, Kathleen; Lopilato, Jane; Wilson, T.

doi: 10.1007/BF01875968pmid: 7003151

p-Nitrophenyl-α-galactoside (α-pNPG) was found to be a substrate for the melibiose transport system ofEscherichia coli. This sugar enters induced cells via the carrier and is split by α-galactosidase to galactose andp-nitrophenol. In mutant cells lacking the α-galactosidase [3H]-α-pNPG accumulated to concentrations 15 times higher than the external medium. The transport of α-pNPG is inhibited by both Na+ and Li+. Na+ (10mm) reduced the Km for α-pNPG from 0.45 to 0.18mm and reduced theV max from 6.7 nmoles/min/mg dry wt to a value of 3.0.