Kinetics of porphyrin accumulation in cultured epithelial cells exposed to ALA.
1. The kinetics of porphyrin accumulation in cultured mammalian epithelial cells (CNCM-I-221) during exposure to ALA was investigated. 2. The total porphyrin synthesized is a function of ALA concentration and the incubation time. The cellular porphyrin content exhibited a saturation pattern, reaching a plateau at about 0.04 fmol porphyrins/cell. A biphasic time-dependent increase in the total porphyrin synthesized was observed. 3. After 3 hr of exposure to ALA the rate of synthesis increased to almost twice the initial rate, reaching between 0.02 and 0.05 fmol porphyrins/cell/hr depending on serum concentration in the medium. 4. Two effects of FBS on ALA-stimulated porphyrin accumulation were observed. Greater total porphyrin synthesis was found when incubations were made in 10% FBS compared to those in 1% FBS. 5. The higher serum concentration also caused a greater release into the medium of the porphyrins generated in the cells with a calculated half-life of 24 min in 10% serum-supplemented medium compared with 62 min in 1% serum. 6. The results obtained from cell synchronization experiments suggest that there is little obvious cell cycle-dependent variation in the synthesis of porphyrins from ALA. 7. The small differences in the intracellular porphyrin content that were observed may be attributed to a slight reduction in the rate of loss of porphyrins in G2/M cells.
Fukuda
H
H
Centro de Investigaciones sobre Porfirinas y Porfirias (CIPYP), Consejo Nacional de Investigaciones Cientificas Tecnicas (CONICET), Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina.
Batlle
A M
AM
Riley
P A
PA
D000622:Aminolevulinic Acid / Q000494:pharmacology*; D000818:Animals; D002453:Cell Cycle / Q000187:drug effects; D002460:Cell Line; D004847:Epithelial Cells; D004848:Epithelium / Q000187:drug effects / Q000378:metabolism; D007700:Kinetics; D011166:Porphyrins / Q000378:metabolism*
D011166:Porphyrins; D000622:Aminolevulinic Acid