NUCLEAR COLOCALIZATION OF PROLACTIN AND THE PROLACTIN RECEPTOR IN RATNB2 NODE LYMPHOMA-CELLS

Previous studies have indicated that prolactin (PRL) interacts with sp ecific, high affinity, immunoreactive binding sites within isolated ra t hepatocyte nuclei. Moreover, endogenous PRL appears to be bound to t his site. However, it remained important to demonstrate nuclear PRL re ceptors and hormonal translocation in an intact cell system. Therefore , we sought nuclear translocation of PRL and its receptor in the nucle us of PRL-dependent Nb2 node lymphoma cells. Utilizing immunofluoresce nce (IF) microscopy, growth-arrested cells were found to constituitive ly express the PRL receptor in the nucleus, and in the membrane/cytoso l compartments. Addition of PRL stimulated rapid hormone internalizati on followed by translocation to the nucleus within 6-12 hrs. The trans location of PRL was found to be reversible and dependent upon ATP. The se results indicate that an early event coupled to the mitogenic actio n of PRL in Nb2 cells is hormone transport to the nucleus during the G 1 and S phases of cell cycle. Once in the nucleus, PRL bound to its re ceptor may directly influence gene transcription.