The isolation of highly 5-hydroxytryptamine concentrated fraction from rabbit duodenal mucous membrane homogenates.

Large amounts of 5-hydroxytryptamine (5-HT) in the mammalian duodenum are found mainly in the enterochromaffin cells. Baker (1) was the first to demonstrate that in the enterochromaffin cells of the dog's duodenal mucosa, 5-HT was stored in large granules which were sedimented in the gravitational field used for the sedimentation of mitochondria. By further equilibrium centrifugation in a sucrose density gradient the granules were partially purified from mitochondria (2). Prusoff (3) reported that even with a two density gradient centrifugation of the mitochondrial fraction succinic dehydro genase (SDH) activity was still found in the fraction that was rich in 5-HT. Therefore, in this paper an attempt has been made to separate 5-HT storage granules from SDH. Attention has also been given to minimizing damage to the granules during separation. For this purpose urografin density gradients have been employed.