Date of Award


Degree Type


Degree Name

Doctor of Philosophy


This project was initiated to obtain a better understanding of the cellular mode of action of the anthracycline drug menogaril. Comparative experiments demonstrated that menogaril was as cytotoxic as adriamycin against parental AUX B1 Chinese hamster ovary cells (CHO), however, multidrug resistant (MDR) CH{dollar}\sp{lcub}\rm R{rcub}{dollar}C5 CHO cells, which are characterized by the overexpression of P-glycoprotein relative to the parental cells, were less resistant to menogaril. When parental and MDR cells were exposed to equitoxic concentrations of both drugs, menogaril accumulated to a higher level, however, both drugs accumulated to a significantly higher level in the MDR cells. Immediately after exposure to either drug, ({dollar}\sp3{dollar}H) -thymidine incorporation was inhibited, whereas ({dollar}\sp3{dollar}H) -uridine and ({dollar}\sp3{dollar}H) -leucine incorporation were altered 48 hours after exposure. Cellular morphology was not altered two hours after treatment with either drug, however, 48 hours after, exposure multinucleated cells were present. These cells contained surface blebs, stress fibers and an increased number of microtubules. Membrane fluidity increased in MDR cells after exposure to either drug but was not altered in the parental cells. Na/K ATPase activity was altered in parental cells after exposure to either drug, whereas neutral amino acid transport was altered 48 hours after exposure. These results suggest that DNA synthesis may be an important site of menogaril cytotoxicity and that perturbations in cell morphology and membrane function may be secondary. Adriamycin increased the rate of oxygen consumption to a greater extent than menogaril which may contribute to the difference in cardiotoxicity between the two drugs. While assessing the effects of both drugs on membrane function it was observed that the amount and rate of accumulation of neutral amino acids was depressed in MDR cells when compared to the parental cells, however, there was no difference in the rate of efflux. Verapamil which reversed the MDR phenotype did not return the kinetics of neutral amino acid transport to parental levels but did alter the transport in both cell lines. Collectively, these results suggest that P-glycoprotein is not directly involved in the altered amino acid transport in MDR cells.



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