DRIVING FORCES OF AMINO ACID TRANSPORT IN ANIMAL CELLS^fn1

Abstract

Our observations on the response of TPP+ uptake into K+-depleted cells on the extracellular K+ concentration and on the addition of ouabain and amino acid appear to provide suggestive evidence of, or are at least consistent with, the operation of a powerful, K+-activated electrogenic pump. They are also consistent with the assumption that in these K+-depleted cells the active uptake of amino acid energized by the electric PD presumably generated by this electrogenic pump. It follows that an energy source other than the electrochemical potential gradient of Na+ ions need not be invoked to explain active amino acid transport with inverted Na+ and K+ distribution. In the presence of an electrogenic cation pump one should expect that owing to the activity of this pump the electrical PD is raised under these conditions to a value outweighing the opposed chemical potential gradient of Na+. The experimental evidence so far available is clearly consistent with such an assumption.

Membrane potential, chloride exchange, and chloride conductance in Ehrlich mouse ascites tumour cells.

“…The values obtained in the present study (-27 + 1 0 mV (n = 74)) correspond to the previously reported values about -24 mV (Lassen et al 1971). Somewhat less negative, stable values (-12 to -14 mV) have been obtained by Smith and coworkers, employing a different technique (Smith & Levinson, 1975;Smith & Adams, 1977), whereas considerably more negative values have been reported based on indirect estimates (Heinz et al 1975(Heinz et al , 1977Burckhardt, 1977).…”

“…(12)), because the measured Vm which may be regarded as the initial value after a sudden change in external K+ concentration, was found to be reasonably constant with time and because the Nernst potentials for C1-(Ec1) and Na+ (ENa) are essentially constant in this region (see Christoffersen, 1973;Lassen, 1977;Lassen, Pape & Vestergaard-Bogind, 1978 Lassen, 1977;Lassen & Rasmussen, 1978). Although there is increasing evidence for the existence of an electrogenic Na+-K+ pump in Ehrlich ascites cells (Heinz et al 1975(Heinz et al , 1977 concentrations of K+, Na+, and Cl-, assuming equal activity coefficients in cell water and in the extracellular medium, and neglecting the available evidence ofintracellular compartmentation of Na+ and Cl- (Smith & Adams, 1977), or nuclear sequestration of these ions (Pietrzyk & Heinz, 1974 (Mills & Tupper, 1975;Tupper, 1975). This component would appear to be small, however, in cells with high intracellular K+ concentration, and suspended in ordinary Ringer solutions (see Fig.…”

Use of a lipophilic cation for determination of membrane potential in neuroblastoma-glioma hybrid cell suspensions

“…The technique involves the use of the permeant lipophilic cation tetraphenylphosphonium (TPP+) which has been used to measure AI in mitochondria (10), Ehrlich's ascites cells (11), and bacteria and bacterial membrane vesicles.$ The use of "lipophilic ions" to measure AI across biological membranes was introduced by Skulachev and Liberman (for review, see ref. 12) and their coworkers in the early 1970s, and this class of compounds has been applied to a number of prokaryotic and eukaryotic systems (10-16, ¶).…”

Cellular energy metabolism, trans-plasma and trans-mitochondrial membrane potentials, and pH gradients in mouse neuroblastoma

“…Membrane potentials have been evaluated by measuring the distribution of radioactively labeled permeant lipophilic ions. This approach was first introduced by Skulachev and coworkers (6)(7)(8) and has been applied to a variety of biological systems (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20). These experiments were carried out at room temperature as described (19,20 Measurements of Energy Parameters.…”