Influence of priming with 5-hydroxytryptophan on APUD characteristics in human small cell lung cancer cell lines

Two established human small cell cancer lines (SCCL) were exposed to 5-hydroxytryptophan (5-HTP) for various time intervals. The levels of l-dopa decarboxylase (DDC), formaldehyde-induced fluorescence (FIF), number and volume density of dense-cored granules, and levels of bombesin-like immunoreactivity (BLI) and of immunoreactive calcitonin (ICT) were examined in controls and after 5-HTP treatment. The levels of DDC and BLI were not changed by 5-HTP treatment, while FIF was significantly increased in all 5-HTP treated groups. Immunoreactive calcitonin was undetectable in all groups including the controls. A quantitative increase in number and volume density of dense-cored granules was measured in one cell line after 18 h of 5-HTP and was accompanied by exocytosis of granules. The data demonstrate that while 5-HTP increased cellular activity in one of the cell lines (increase in number of densecored granules and evidence of secretion), not all of the measured parameters of APUD cells correlate under these experimental conditions.