Changes in free amino acid concentrations in tissues of the freshwater pulmonate, Helisoma duryi, during hypertonic stress

Abstract

1. 1. Intracellular osmoregulation by free amino acids (FAA) of the freshwater pulmonate snail, Helisoma duryi, is demonstrated. 2. 2. Alanine, glutamate, aspartate, glutamine, glycine and serine were major components of the FAA pool, which increased in response to hypertonic stress. 3. 3. Total FAA levels were increased from 10 μmol/g dry tissue to 40 μmol/g dry tissue in kidney and to 60 μmol/g dry tissue in foot, when the snails were transferred to hypertonic medium (190 mOsm/kg H 2O). 4. 4. The FAA accounted for only a small part of the total osmotic increment. 5. 5. Isolated kidneys incubated in vitro with hypertonic saline showed a pattern of FAA accumulation similar to that in situ. Whole brain extracts did not affect the hypertonically-induced FAA accumulation in the isolated kidney.