STEREOSPECIFICITY OF AMINE UPTAKE MECHANISM IN NERVE GRANULES

¹ Department of Physiology, Karolinska Institutet, Stockholm, Sweden

Uptake of labeled dl-NE was measured in isolated nerve granules on incubation with nonlabeled l-, dl-or d-NE and tracer amounts of H³-dl-NE, followed by resuspension in a NE-free medium and reincubation.

The specific activity ratio (radioactivity per unit NE in the granules over that of the original suspension medium) was low and constant throughout the second incubation in the l-NE series, intermediate and constant in the dl-NE series, and highest in the d-NE series.

It was concluded from the data obtained that the nerve granules show a distinct preference for l-NE and that this bias may be expressed as an "affinity ratio," l-NE/d-NE, which under certain assumptions could be calculated as having a mean value of 5.9/1.

The greater "protective effect" (capacity to maintain a high NE concentration in the granules) of l-NE was confirmed and found to be about five times as high as that of d-NE.