FLUORESCENCE MICROSCOPY OF 5-HTP TURNOVER IN EXOCRINE PANCREAS OF MICE AND RATS

The turnover of l-5-HTP, d-5-HTP and 5-HT in the exocrine pancreas have been studied by means of the fluorescence method of Falck and Hillarp. l- and d-5-HTP are easily taken up by the acinar cells, whereas 5-HT seems to pass into the cells only to a minor extent. After the administration of l-5-HTP (and in some cases after 5-HT administration), specific fluorescence is seen in the form of apically located granules (probably identical with the zymogen granules) for a short period, which is prolonged, if the animals are pretreated with a MAO inhibitor. Decarboxylase inhibition prevents the appearance of these fluorescent granules. Administration of d-5-HTP does not give rise to this granular fluorescence but to a diffuse fluorescence throughout the cells. Thus, there are reasons to assume that the granular fluorescence derives from 5-HT. The results obtained in this work correspond well with those from a similar study with l-DOPA and some of its analogues. © 1969 Springer-Verlag.