ISOSMOTIC REGULATION IN ISOLATED SURVIVING NERVES OF ERIOCHEIR SINENSIS MILNE EDWARDS

1. 1. The free amino-acid level of isolated nerves of a freshwater Eriocheir increases when they are transferred to a saline corresponding to the blood concentration of animals adapted to sea water. The free amino acid concentration decreases when nerves isolated from a sea-water adapted animal are placed in a fresh-water saline. The total protein concentration remains unchanged during such transfers. 2. 2. The concentrations of tyrosine, phenylalanine, valine, leucine or isoleucine appear to be regulated by a mechanism involving modifications of the permeability of the nerve membrane to these amino acids. 3. 3. The concentration of the so-called non-essential amino acids is regulated by a mechanism involving modifications of their metabolism. It looks as if this mechanism does not imply a modification of the steady-state between amino acids and proteins but rather a modification of the activity of the pathways responsible for the biosynthesis and the degradation of these amino acids. 4. 4. The two mechanisms involved in the regulation of amino-acid level seem to be at play in the control of proline concentration. 5. 5. Isolated nerve, when subjected in vitro to an osmotic stress, thus responds, qualitatively at least, in the same way as in the intact animal. © 1969.