INFLUENCE OF EXTRACELLULAR ION CONCENTRATION ON THE INTRACELLULAR ACCUMULATION OF ADRIAMYCIN

The cytotoxic action of adriamycin is influenced by its intracellular accumulation. Therefore, it is important to clarify the mechanisms of adriamycin influx and efflux. In the present study, the influence of t he extracellular KCl and Ca2+ concentration the extracellular pH and t he presence of NaHCO3 on the ADR accumulation was investigated in orde r to study the mechanisms in ADR accumulation influenced by ions. The extracellular KCl concentration did not affect the intracellular ADR a ccumulation This suggests the cell membrane potential does not affect the ADR accumulation since it is influenced by the KCl concentration. The intracellular intensity of fluorescence of Fluo3 an indicator of C a2+, increased between 0 and 20 mM of the extracellular concentration of Ca2+ ion. However; the ADR accumulation did not change between 0 an d 20 mM of the extracellular concentration of Ca2+. This indicates tha t the extracellular concentration of Ca2+ does not affect the ADR accu mulation under physiological conditions since 20 mM of Ca2+ is beyond normal physiological conditions. Further, the intracellular fluorescen ce of Fluo3 decreased as inn-easing the extracellular pH. In contrast, the ADR accumulation increased as increasing the extracellular pH. Th ese suggest that the ADR accumulation increases as decreasing the intr acellular Ca2+ as changing the extracellular pH- In wild type strain, the ADR accumulation did not change by the extracellular pH in the abs ence of NaHCO3, but increased as increasing the extracellular pH in th e presence of NaHCO3. This suggests that the ADR accumulation in the w ild type strain is influenced by NaHCO3 but the extracellular pH. In t he ADR-resistant strain, the ADR accumulation decreased as increasing the extracellular pH regardless of NaHCO3. However, the accumulation o f ADR increased as increasing the extracellular pH when the adjustment of pH was carried out with IN HCl. This suggests that Cl- may play an important role in the ADR influx in the ADR-resistant strain.