CHARACTERIZATION OF A DIAMINE EXPORTER IN CHINESE-HAMSTER OVARY CELLSAND IDENTIFICATION OF SPECIFIC POLYAMINE SUBSTRATES

Export of the diamine putrescine was studied using inside-out plasma m embrane vesicles prepared from Chinese hamster cells, Putrescine uptak e into vesicles was a saturable and an ATP- and antizyme-independent p rocess, Excess amounts of a series of diamines or mono acetyl spermidi ne, but not monoacetyl putrescine, spermidine, or spermine, inhibited putrescine transport. Putrescine uptake into vesicles prepared at pH 7 .4 was suppressed at pH 5, compared with pH 7.4; was stimulated simila r to 2.5-fold at pH 7.4 in vesicles prepared at pH 6.25, compared with vesicles prepared at pH 7.4; and was not inhibited by valinomycin in the presence of potassium ions, Reserpine and verapamil blocked [H-3]p utrescine uptake into inverted vesicles. Verapamil treatment caused an increase in intracellular contents of putrescine, cadaverine, and N-8 -acetylspermidine, in unstressed proliferating cells, or of N-1-acetyl spermidine, in cells subjected to heat shock to induce acetylation of spermidine at N-1, These data indicate that putrescine export in Chine se hamster cells is mediated by a non electrogenic antiporter capable of using protons as the counter ion. Physiological substrates for this exporter include putrescine, cadaverine, and monoacetyl spermidine an d have the general structure NH3+-(CH2)(n)-NH2 + R at acidic or neutra l pH.