Catecholamine Biosynthetic Enzymes in Pancreatic Islet Cells

Publisher Summary This chapter elaborates the catecholamine biosynthetic enzymes in pancreatic islet cells. Pancreatic islet tissue from several sources was examined for tyrosine hydroxylase, and l -aromatic amino acid decarboxylase activity. Isolated pancreatic islets were obtained by collagenase treatment of pancreas from albino rabbits, pigmented, and albino guinea pigs and golden hamsters. The presence of significant l -aromatic amino acid decarboxylase activity in the islets of all the species suggest that most, or all pancreatic islet tissue can readily convert l -dopa, or 5-hydroxytryptophan to their appropriate monoamines, and thereby increase intracellular pools of these amines when exposed to sufficient precursor. The absence of measureable tyrosine hydroxylase activity in isolated hamster, and rabbit islets might be expected, because these islets ordinarily do not show intracellular monoamines by histochemical fluorescent studies. In contrast, the failure to demonstrate tyrosine hydroxylase activity in isolated guinea pig islets was unexpected, because these islets have been shown to contain considerable dopamine, and serotonin.