The Distribution of Radioligand Binding Activity and 5′‐Nucleotidase Activity in Bovine Caudate Nucleus Subcellular Fractions

Abstract

The distribution of 5''-nucleotidase activity dopaminergic [3H]spiperone binding sites and [3H]quinuclidinyl benzilate (QNB) binding sites in different subcellular fractions of bovine caudate nucleus was studied. Each activity was enriched in a microsomal (P3) preparation from that tissue. The microsomal preparation was further fractionated by different techniques. The P3 fraction, or a sonicated P3 fraction, was fractionated on a discontinuous sucrose density gradient, or the P3 fraction, or a digitonin-pretreated P3 fraction, was fractionated on a continuous sucrose density gradient. 5''-Nucleotidase activity does not cofractionate with radioligand binding activity, although no difference between the distributions of [3H]spiperone binding and [3H]QNB binding were seen. The 2 radioligand binding activities are located on nonglial membranes.