Proximal tubule dopamine histofluorescence in renal slices incubated with L-dopa

Renal cortex slices were incubated with amine precursors L-dopa, or L-5-HTP. Localization of synthesized amines, dopamine or serotonin, was examined by means of histofluorescence methods. Formaldehyde-induced fluorescence was present in the proximal convoluted tubule and not in the pars recta or other segments of the tubules after incubation in the presence of 10(-3) to 10(-7) M L-dopa. Tubule-induced fluorescence was not seen in the presence of an inhibitor of dopa-decarboxylase or in the absence of sodium. It was independent of innervation. It is concluded that dopamine and serotonin are accumulated and likely formed within proximal convoluted tubular cells.