Ontogeny of (--)-[3H]norepinephrine uptake properties of synaptic storage vesicles of rat brain.
The ontogeny of[3H]norepinephrine uptake mechanisms has been examined in synaptosomes and storage vesicles isolated from rat whole brain. The [3H]norepinephrine accumulated by synaptosomes was low in neonates, but reached adult levels by 15 days of age. In contrast, development of[3H]norepinephrine uptake into isolated rat brain storage vesicles was not complete until 38 days of age. Kinetic analysis of the developing vesicular uptake mechanism revealed no change in Km, while maximal uptake increased progressively from birth to maturity. Storage vesicles from immature and adult rats exhibited similar energy requirements for uptake as determined by their dependence on ATP-Mg2+ concentration; furthermore, the degree of inhibition of [3H]norepinephrine uptake by other amines was the same in both vesicle preparations. Thus, storage vesicles isolated from adult and developing rats display an in vitro[3H]norepinephrine uptake mechanism with properties that are kinetically and pharmacologically similar. The results suggest that, while the number of storage vesicles in the central nervous system increases during development, those vesicles that are present possess a fully functional amine uptake system.
Kirksey, DF; Seidler, FJ; Slotkin, TA
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