Adenosine Triphosphate-Dependent Calcium Uptake of Synaptic Vesicle Fraction is Largely Due to Contaminating Microsomes

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Abstract
Ca2+ uptake by synaptic vesicle fractions isolated from bovine caudatolenticular nuclei and from rat brain was studied. The purified vesicle fractions from both materials took up very little Ca2+ even in the presence of ATP and Mg2+, but the crude fractions took up Ca2+ actively, showing the maximum uptake around pH 7.0. Since the crude fractions were contaminated by microsomes, which are known to accumulate Ca2+ actively (Yoshida, H., Kadota, K., & Fujisawa, H. (1966) Nature 212, 291–292; Otsuka, M., Ohtsuki, L, & Ebashi, S. (1965) J. Biochem. 58, 188–190), the active uptake of Ca2+ appeared to be largely, if not wholly, due to microsomal contamination.