Related Experiment Video
Updated: Oct 20, 2026

Introduction to Solid Supported Membrane Based Electrophysiology
Published on: May 11, 2013
Substrate specificity of the mammary tissue anionic amino acid carrier operating in the cotransport and exchange
I D Millar1, D T Calvert, M A Lomax
1Hannah Research Institute, Ayr, UK.
Abstract:
The substrate specificity of the rat mammary tissue high affinity, Na+-dependent anionic amino acid transport system has been investigated using explants and the perfused mammary gland. D-Aspartate appears to be transported via the high affinity, Na+-dependent L-glutamate carrier. Thus, D-aspartate transport by rat mammary tissue was Na+-dependent and saturable with respect to extracellular D-aspartate with a Km and Vmax of 32.4 microM and 49.0 nmol/2 min per g of cells respectively. The uptake of D-aspartate by mammary explants was cis-inhibited by L-glutamate and L-aspartate, but not by D-glutamate. L-glutamate uptake by mammary tissue explants was cis-inhibited by beta-glutamate, L-cysteate, L-cysteine sulfinate and dihydrokainate but not by DL-alpha-aminoadipate. In addition, dihydrokainate, but not DL-alpha-aminoadipate inhibited D-aspartate and L-glutamate uptake by the perfused gland. D-Aspartate efflux from mammary tissue explants was trans-accelerated by external L-glutamate in a dose-dependent fashion (50-500 microM). The effect of L-glutamate on D-aspartate efflux was dependent on the presence of extracellular Na+. D-Aspartate, L-aspartate and L-cysteine sulfinate (at 500 microM) also markedly trans-stimulated D-aspartate efflux from mammary tissue explants. In contrast, L-cysteine. D-glutamate, L-leucine, dihydrokainate and DL-alpha-aminoadipate were either weak stimulators of D-aspartate efflux or were without effect. D-Aspartate efflux from the perfused mammary gland was trans-stimulated by L-glutamate but not by D-glutamate and only weakly by L-cysteine (all at 500 microM). It appears that the mammary tissue high affinity anionic amino acid carrier can operate in the exchange mode with a similar substrate specificity to that of the co-transport mode.
More Related Videos
Related Concept Videos
Secondary Active Transport
Membrane Transporters
Transporters are mainly composed of alpha-helices, built from bundles of ten or more helices traversing the plasma membrane. The solute-binding sites are located midway, where some of the helices are broken or distorted, making space for the binding site through...
Secondary Active Transport
Secondary Active Transport
Drug Absorption Mechanism: Carrier-Mediated Membrane Transport
Facilitated diffusion is a passive process that utilizes human Solute Carrier (SLC) transporters. These transporters bind to the drug, undergo structural...
Carrier-Mediated Transport
Active transport involves two types of membrane-spanning transporters: uptake and efflux. Uptake transporters are expressed in the small...

