Accumulation of chemostimulatory amino acids by a sedimentable fraction isolated from olfactory rosettes of rainbow trout (Salmo gairdneri).

The accumulation of amino acids by a sedimentable fraction from olfactory rosettes of rainbow trout (Salmo gairdneri) was examined to determine the correspondence with established criteria for receptors. Physical parameters such as saturability, reversibility, affinity and quantity of sites were reasonably consistent with receptor criteria. The kinetics of association were slow and not in accord with values expected of sensory receptors. Accumulation correlated with electrophysiological effectiveness for most amino acids. The correlation was tissue specific, not being evident in brain or gill. Denervation experiments showed that high-affinity accumulation depended upon the presence of neuronal elements in the olfactory mucosa. Inhibition studies with amino acids and analogues generally indicated good correspondence with previous electrophysiological findings. Experiments with transport inhibitors, lack of Na+, counter-transport and increasing osmotic strength showed some involvement of amino acid transport. Inconsistencies between the various aspects of amino acid accumulation by the sedimentable fraction and electrophysiological response preclude unequivocal classification of the accumulation as representing olfactory receptors.