Abstract
The effect of melphalan, an antineoplastic alkylating agent, on the activity of delta -aminolevulinic acid synthetase (ALA-S) was studied. When given in a single oral dose to male rats, ALA-S activity in the spleen rapidly declined, reaching 9% of controls 7 days after administration. After melphalan administration, a gradual loss in spleen weight was observed until day 10, followed by a rebound increase in spleen weight at day 15. Spleen heme oxygenase activity was induced to 243% of controls 7 days after melphalan administration. Bone marrow ALA-S activity declined to 38% of controls 3 days after treatment, followed by a return to controls after 7 days. The return to control values at day 15 was accompanied by a shift in the differential white blood cell count to the segmented form. Red blood cell counts and hemoglobin content were decreased to 77% of controls at day 7. Liver ALA-S was not appreciably affected by melphalan except for a decrease to 56% of controls at day 7.