SUBCELLULAR-DISTRIBUTION OF NORADRENALINE IN GUINEA-PIG CEREBRAL-CORTEX AND SPLEEN

Abstract— The distribution of noradrenaline (NA) in subcellular fractions of guinea‐pig cerebral cortex and spleen was determined by differential and density gradient centrifugation. Of the primary fractions, the microsomal fraction from both tissues was enriched in NA, that of the spleen having the higher specific activity. Microsomal fractions were therefore placed on gradients and NA determined in the subfractions since these fractions appeared suitable preparations in which to search for discrete populations of vesicles. So that the non‐occluded micro‐particulate bound noradrenaline (MPBNA) content of gradient subfractions could be measured, [3H]NA was used to control for the diffusion and or adsorption of free NA, and occluded lactate dehydrogenase was used to estimate the amount of entrapped MPBNA and soluble NA. Non‐occluded MPBNA on gradients from microsomal fractions of cerebral cortex formed a single peak mainly in subfraction F (0.6‐0.8 m‐sucrose). Spleen microsomal fractions, however yielded two peaks of MPBNA. one in sub‐fractions D to G (0.4‐1.0 m‐sucrose) and the other in sub‐fraction J (1.4 m‐sucrosc); electron microscopy showed that the latter subfraction contained large vesicles. Since there were unexpectedly small amounts of MPBNA in microsomal subfractions D and E of cerebral cortex, the synaptosome fraction was investigated. Following water treatment of synaptosomes. MPBNA formed a peak in subfraction E (0.4‐0.6 m‐sucrose) with smaller amounts in subfractions D and F (0.4 and 0.6 0.8 m‐sucrose). Copyright © 1979, Wiley Blackwell. All rights reserved