Effect of 1-DOPA on calcitonin secretion by thyroid C cells.

After administering 1-DOPA for 7 d a decreased number of secretory granules as well as pronounced rough endoplasmic reticulum and Golgi apparatus were noted in C cells. A single dose of 1-DOPA did not inhibit C cell stimulation induced by a single dose of calcium gluconate. On the other hand, parallel administration of alpha-methyl-DOPA and calcium gluconate did not decrease the number of C cell secretory granules, which were observed after administration of calcium gluconate alone. The data suggest that the presence of DOPAmine (formed the 1-DOPA) in the secretory granules is a prerequisite for normal functioning of secretory processes in thyroid C cells.