Effect of chloroquine on membrane permeability in yeast--release of cellular coproporphyrin.

1. The influx and efflux of labelled substances with and without chloroquine was studied in yeast cells. 2. The uptake of delta-aminolevulinic acid by Saccharomyces cerevisiae is characterized by a KT of 3-4 mM and Jmax of 1.0-1.2 mumol min-1 g dry weight-1. 3. A method for loading yeast with labelled coproporphyrin is suggested. 4. The uptake of sorbitol and coproporphyrin was slightly stimulated, while the uptake of 6-deoxyglucose was slightly, that of 2-aminoisobutyric acid and leucine strongly inhibited by chloroquine. 5. The efflux of coproporphyrin, 2-aminoisobutyric acid and sorbitol was stimulated while that of leucine was not influenced by chloroquine. 6. The result showed that chloroquine influenced directly but nonspecifically the membrane permeability, apparently mainly that of the vacuolar membrane.