Fig. 1. Transfection of the rat PRL-R into BaF-3 cells. A, BaF-3 and W53 cells (107 were biosynthetically labeled with L-[35S]methionine and L-[35S]cysteine (200 µCi/ml) for 2 h. The supernatants from cell lysates were immunoprecipitated sequentially with normal mouse serum, as preimmune control, and then with the anti-PRL-R U5 mAb. The immune complexes were analyzed by SDS-9% PAGE and fluorography. Molecular markers (in thousand) are at the left, and the position of the PRL-R is indicated. B, W53 cells were seeded at 104 cells/well in 96-microwell plates in complete medium supplemented with PRL. After 48 h, cell cultures were pulsed overnight with 1 µCi of [3H]thymidine, harvested [3H]-TdR), and the incorporated radioactivity was measured in a scintillation counter (35,591 ± 818 cpm in BaF-3 cells = 100%). Bars, SD.