Driving forces for the uphill transport of amino acids into epidermal brush border membrane vesicles of the sea anemone, Anemonia sulcata (Cnidaria, anthozoa)

Abstract

1. 1. The transport of amino acids into membrane vesicles prepared from epidermal tentacle tissue of the sea anemone, Anemonia sulcata, depends on an electrochemical potential difference caused, e.g. by sodium chloride gradients. 2. 2. Potassium or choline chloride gradients energized the transport less effectively than sodium chloride gradients. Both Na +-ions and Cl −-ions were required for the amino acid transport. 3. 3. The uphill transport of amino acids along the downhill movement of driver ions (sodium chloride gradient conditions) was characterized by an overshoot; under sodium chloride equilibrium conditions, however, an accumulation of amino acids within the vesicles could not be measured. 4. 4. Potassium diffusion potentials in combination with valinomycin indicated that hyperpolarization (vesicle inside negative) and hypopolarization (vesicle inside positive) enhanced or depressed the accumulation of amino acids within the vesicles. 5. 5. Being at the phylogenetic base of the Eumetazoa, cnidarians show characteristics for the transmembrane transport of amino acids comparable to those established for vertebrates.