HUMAN PROMYELOCYTIC CELL-LINE HL-60 HAS THE SPECIFIC BINDING-SITES FOR PROLACTIN AND ITS ORNITHINE DECARBOXYLASE, DNA-SYNTHESIS AND CELLULAR PROLIFERATION ARE INDUCED BY PROLACTIN

Human prolactin (hPRL) induced ornithine decarboxylase (ODC) activity, subsequently DNA synthesis and cellular proliferation on human promye locytic cells, HL60, cultured in a serum-free medium. HL60 cells had 2 100 specific binding sites for hPRL per cell, showing a dissociation c onstant of 1.1 x 10(-10) M. Binding of I-125-PRL to the cells was not blocked by simultaneous addition of human growth hormone. ODC activity and DNA synthesis were activated maximally at 5 and 20 h, respectivel y, after the addition of 0.05 nM hPRL. These effects of PRL on cellula r proliferation, ODC activity and DNA synthesis were abolished by the simultaneous addition of anti-hPRL antibody. Simultaneous addition of an irreversible inhibitor of ODC, difluoromethyl ornithine (DFMO), als o abolished the inductions of ODC and DNA synthesis by hPRL. The inhib itory effect of DFMO on hPRL-induced DNA synthesis was reversed by the addition of putrescine to the culture medium. These results suggest t hat hPRL binds to the prolactin receptor on HL60 cells and induces ODC activity to increase cellular polyamine levels, which eventually stim ulates DNA synthesis and cellular proliferation.