CHARACTERIZATION OF THE CATECHOLAMINE EXTRANEURONAL UPTAKE, CARRIER IN HUMAN GLIOMA CELL-LINES SK-MG-1 AND SKI-1 IN RELATION TO (2-CHLOROETHYL)-3-SARCOSINAMIDE-1-NITROSOUREA (SARCNU) SELECTIVE CYTOTOXICITY

Transport of (2-chloroethyl)-3-sarcosinamide-1-nitrosourea (SarCNU) an d (-)-norepinephrine was investigated in SarCNU-sensitive SK-MG-1 and -resistant SKI-1 human glioma cell lines. [H-3]SarCNU influx was inhib ited by SarCNU, sarcosinamide, and (+/-)-epinephrine in SK-MG-1 cells with competitive inhibition observed by (+/-)-epinephrine (K-i = 140 /- 12 mu M) and (+/-)-norepinephrine (K-i = 255 +/- 41 mu M). No effec t on influx was detected in SKI-1 cells. [H-3](-)-Norepinephrine influ x was linear to 15 sec in both cell lines and temperature dependent on ly in SK-MG-1 cells. Influx of [H-3](-)-norepinephrine was found to be saturable in SK-MG-1 (K-m = 148 +/- 28 mu M, V-max = 1.23 +/- 0.18 pm ol/mu L intracellular water/sec) but not in SKI-1 cells. In SK-MG-1 ce lls, [H-3](-)-norepinephrine influx was found to be inhibited competit ively by (-)-epinephrine (K-i = 111 +/- 7 mu M) and SarCNU (K-i = 1.48 +/- 0.22 mM). Ouabain and KCl were able to inhibit the: [H-3]norepine phrine influx in SK-MG-1 cells, consistent with influx being driven by membrane potential. Several catecholamine uptake(2) inhibitors were a ble to reduce significantly the influx of [H-3](-)-norepinephrine and [H-3]SarCNU with no inhibition by a catecholarnine uptake(2) inhibitor . These findings suggest that increased sensitivity of SK-MG-1 to SarC NU is secondary to enhanced accumulation of SarCNU mediated via the ca techolamine extraneuronal uptake(2) transporter, which is not detectab le in SKI-1 cells. The introduction of SarCNU into clinical trials wil l confirm ii increased uptake via the catecholamine extraneuronal upta ke(2) transporter will result in increased antitumor activity.