Exocytosis as a possible mechanism for the secretion of coproporphyrin from a chloroquine-treated yeast.

Chloroquine, which is known to be concentrated in intracellular acid vesicles, stimulates the release of porphyrins from yeast. Experiments with normal baker's yeast Saccharomyces cerevisiae and the sec-1 mutant, with suppressed exocytosis, showed that the release of porphyrins was stimulated more in normal yeast than it was in the mutant. It is suggested that chloroquine stimulates the exocytosis of porphyrins.